We go "every" T-giving (this upcoming one will be our 6th)...it's the most crowded of all the times we go (including this year's first-ever March spring break trip)...we booked at 11 months (day-by-day...probably wasn't needed, as we booked at SSR...but the year we bought
DVC (in June), we had to W/L to get our SSR studio)...
As a previous poster suggested, parks and rides, using fast pass strategies, aren't bad at all from opening til 11 or so...by noon, it's packed...late afternoons & evenings are more crowded than mornings, but not as bad as early to mid afternoon...Monday & Tuesday are noticeably less crowded than Wed-Thurs-Fri & Sat...crowds lighten up again by Sunday...
Downtown Disney at night is wall-to-wall...we try to do it at lunch time instead...
But the atmosphere is phenomenal...the holiday decorations are breathtaking in the parks and at the resorts...we absolutely love it and by now it just wouldn't be T-giving for us if we didn't go to Disney!
Of course, now that we have DVC we go to WDW a lot...so we have no "need" to commando or do any particular ride...last T-giving I rode only one ride in an entire week...not that I "couldn't"--just preferred to stroll and look and absorb the atmosphere...it was one of our best trips ever!