I received my PRO 5 yesterday and gave it a quick overview. I got the chance to try it out this evening so I could give you a review. I'll keep it brief. I love my own writing, but I suspect other people might not quite as much. 
The sander comes in a SYS 2, like all the Festool sanders I've seen. For the Limited edition they've put it in a blue box with green latch and handle, meant to give it the same color scheme as the tool itself, I think. The blue looks considerably darker to me, but as the old saying goes, so what?
The tool is in the usual molded tray with plenty of that "wasted space" that non-Festoolians complain about. I was able to neatly store 200 sheets of Granat in the box along with the tool, edge guard, and power cord. Space is only wasted if you don't use it.
The PRO 5 comes with a replacement for your 27mm hose connector. Why? Because the SYS 5 has a new dust-extraction connector with a locking bayonet connection. This is a major plus. The new hose connector works like the old one on old-style tool connectors and vice versa. It took me less than a minute to swap out the connectors. Dust collection is up to the usual Festool standards.
I gave the tool a brief trial run, sanding a scrap of plywood using the sequence 60-80-120-180-220. The tool glided over the work piece as we've come to expect from Festool finish sanders and was the usual pleasure to use. Noise and vibration were about the same as on my existing DTS 400. The rubberized grip, however, was a nice feature that allowed me to use a lighter grip, which made the work less tiring and meant that there was a little less felt vibration. Another ergonomic touch is that Festool has moved the speed control to the side of the tool, which should eliminate the unintentional speed changes that have been an annoying problem up to now (for me, at least).
Workflow is also improved by the addition of a brake. The pad doesn't come to an immediate dead stop when you turn the tool off, but it does come very close. In fact, I'd say it takes about the time that passes between flipping the switch and setting it down. Which brings me to the switch. It's a little larger than the old one, but the small change in size (and shape) has made it noticeably easier to use. Another ergonomic plus.
Finally, the quality of the work is exactly what you would expect from a Festool finish sander. In other words, perfect. There were no visible swirls, nor did I find any swirls when inspecting the finished piece under an 8X magnifier. This is very boring because I didn't get to develop that close personal relationship with the wood that I get from doing a last, hand sanding; but I think you'll agree it's all for the best.
So, in summary, the improvements are mostly ergonomic and genuinely improve the ease of use of the tool, but there is also a noticeable increase in power. Festool has done it again! [smile]
UPDATE
In addition to the features I discussed in the original review the PRO 5 includes an edge guard. This attaches easily and, it seemed to me, more securely that the edge guard on my RO 125.
Most important to many people will be the fact that this model is 25% more powerful than its predecessor the ETS 400 (250W vs 200W). The difference is really noticeable. Even with its small (2mm) stroke, I was impressed with how quickly it cut.
The dust bag has been dropped from this model. A new dust bag with bayonet connector and long-life bag is available separately.
Abridged edition, with improvements rated + or ++

The sander comes in a SYS 2, like all the Festool sanders I've seen. For the Limited edition they've put it in a blue box with green latch and handle, meant to give it the same color scheme as the tool itself, I think. The blue looks considerably darker to me, but as the old saying goes, so what?
The tool is in the usual molded tray with plenty of that "wasted space" that non-Festoolians complain about. I was able to neatly store 200 sheets of Granat in the box along with the tool, edge guard, and power cord. Space is only wasted if you don't use it.
The PRO 5 comes with a replacement for your 27mm hose connector. Why? Because the SYS 5 has a new dust-extraction connector with a locking bayonet connection. This is a major plus. The new hose connector works like the old one on old-style tool connectors and vice versa. It took me less than a minute to swap out the connectors. Dust collection is up to the usual Festool standards.
I gave the tool a brief trial run, sanding a scrap of plywood using the sequence 60-80-120-180-220. The tool glided over the work piece as we've come to expect from Festool finish sanders and was the usual pleasure to use. Noise and vibration were about the same as on my existing DTS 400. The rubberized grip, however, was a nice feature that allowed me to use a lighter grip, which made the work less tiring and meant that there was a little less felt vibration. Another ergonomic touch is that Festool has moved the speed control to the side of the tool, which should eliminate the unintentional speed changes that have been an annoying problem up to now (for me, at least).
Workflow is also improved by the addition of a brake. The pad doesn't come to an immediate dead stop when you turn the tool off, but it does come very close. In fact, I'd say it takes about the time that passes between flipping the switch and setting it down. Which brings me to the switch. It's a little larger than the old one, but the small change in size (and shape) has made it noticeably easier to use. Another ergonomic plus.
Finally, the quality of the work is exactly what you would expect from a Festool finish sander. In other words, perfect. There were no visible swirls, nor did I find any swirls when inspecting the finished piece under an 8X magnifier. This is very boring because I didn't get to develop that close personal relationship with the wood that I get from doing a last, hand sanding; but I think you'll agree it's all for the best.
So, in summary, the improvements are mostly ergonomic and genuinely improve the ease of use of the tool, but there is also a noticeable increase in power. Festool has done it again! [smile]
UPDATE
In addition to the features I discussed in the original review the PRO 5 includes an edge guard. This attaches easily and, it seemed to me, more securely that the edge guard on my RO 125.
Most important to many people will be the fact that this model is 25% more powerful than its predecessor the ETS 400 (250W vs 200W). The difference is really noticeable. Even with its small (2mm) stroke, I was impressed with how quickly it cut.
The dust bag has been dropped from this model. A new dust bag with bayonet connector and long-life bag is available separately.
Abridged edition, with improvements rated + or ++
- Improved hose connector ++
- Rubberized housing +
- Relocated speed control +
- Modified power switch +
- Edge guard +
- Motor brake ++
- Increased power ++