Hello,
just wanted to chime in with my long term user experience of the KSS300.
I have the kit with the Flexirail in the Sys III. Also, I bought a short Mafell 800mm fixed rail for it, which most people assume that the KSS300 won't fit, but it does. You will lose a few mm in cutting depth vs the Flexirail though.
I have been doing a long term project building a fairly large recording studio and the KSS300 has been around the whole project. Since I had the TS55 with rails up to 3000mm on site the KSS300 has been on stand by for the most part.
However when it came down to flooring and breaking down sheet goods the KSS300 has proved its worth both on and off the rail as well as for plunge cuts in roof panels for lighting installations. Very versatile and I got comfortable doing plunge cuts with it and even did a few sans rail, which all worked fine. For flooring it has been a godsend to be able to cut down the 14mm massive oak flooring just using the short rails, including angled cuts, on top of the Festool vac.
The Flexirail works fine, and in some instances great. However on 600mm panels the Flexirail is just a little too long so you have to slide it back a little and balance it before committing to the cut or else you can't line up the rail to the end markings as the Flexirail bulges. I didn't bring the short rail so it was my own fault. I wish I had the guts to cut down a Flexirail to around 850mm for those cuts as 600mm width goods are common over here. For longer cuts (longer than the Flexiral allows) the Flexirail works fine but it can be a little cumbersome if space is cramped. The quality of cut is very fine but the precision takes a slight beating when you have to cut really long pieces. In my case the level of precision is still more than good enough but if I were to cut down a panel to strips the accumulative error might have been a problem.
Another problem is "handymen" borrowing the Mafell and failing to line up the saw properly on the Flexirail cutting INTO THE RAIL [eek] making a dent in the rail and forcing me to replace the cutting strip. There was no replacement Mafell (red) strip readily available so I had to replace it with the Festool transparent cutting strip. I was concerned that the Festool strip would not stay put on the steel Flexirail when folded but leaving it to cure overnight I had no problems (also, I thoroughly removed old strip residue and cleansed the Flexirail prior to replacement). It seems to stay on and except for the customer having to pay for a new saw blade and the replacement strip all is in working order. The Handyman is banned from using the KSS300 though, for life.
The problem for him and one of the few nitpicks I have with the KSS300 is that the blade keeps turning for quite a while since there is no engine/blade brake on the saw. You have to be a little patient after each cut and allow for the blade to come to a full stop when using the Flexirail.
When using the short track you can just slide out after the cut and tilt it away with the blade running. After many cuts the blade guard got stuck so I needed to clean and check that after almost putting the saw down with the blade (slowly, but still) running. I use a small piece of OSB/Plywood when flooring so I always put the saw down on that anyway, but a potential hazard it is.
Also, I replaced the a/c cord with a Festool Plug-In connector, which works like a charm.
Another nitpick is that you need both hands before doing a plunge cut. If you want to cut a hole in a board and you have carefully laid out the Flexirail you can't keep one hand on the rail but have to use both hands to release the blade guard and mount the saw on the rail. It is a little awkward and takes a little longer than on a fixed rail. Also, you can easily have the saw pop out of the guide ridges when placing it down whilst working the blade guard so that is cause for concern, it would be sad to start plunging slightly into the rail [scared] when you think you are good to go.
All in all I am very pleased with it and have done a whole kitchen with panels, flooring and cutting a 38mm oak bench top using only the KSS300, though the 38mm was at the very limit of how deep a cut I could make with the Flexirail. Cutting thinner panels with the short track freehand can cause blade binding if you are not careful with how you press the short track against the panel, it easily deflects a little under pressure but after a while you get used to it and can counter that. I wish it would be more stable though.
I don't know if pictures would make anyone happy, but I might be able to rustle up some.
/ Henrik