I've lurked for a little while...I'll tell my Festool story, because it is a bit accidental. 2 years ago we just started doing up
another house. As I screwed down the floor boards of the last one, I promised myself a decent box of bits for the DeWalt cordless I was using. I saw the Centrotec set, and for some reason I bought it - it was on special offer (about £210 as I recall) and I thought, "stuff it, I've earned a decent set".
So I got home, and found that the chucks didn't fit on my DeWalt. Ha ha. Actually, nothing fitted. I could see it was terribly clever, and I was intrigued. So I bought a C12.

Brilliant combination, and I've used both today for building stud walls. The DeWalt is still going as well, a good drill, very heavy with a crude clutch, but great for countersinking a bazillion holes in floorboards.
Once I had the C12, it's all been downhill from there. TS75, rails, RS100 and RS400 sanders, an OF1010...and last week, a Kapex. If my Trend vac explodes (that thing has been through heck and back....), then a CTM36 will be on the list.