I also went from 50D to 7D and have been shooting with a pair of them for a couple years. It's a sturdier feeling camera, great viewfinder, good for about a stop higher ISO than I would use on 50D.
I get a kick out of the "faster AF" comments. Actually, lab tests of the 50D and 7D showed the 50D is actually slightly faster to acquire lock (One Shot)... but we're talking a few milliseconds so you'd never notice it in the field. The difference is that the 7D tracks better in AI Servo, which is pretty much impossible to quantify and compare with much accuracy. I just know from using the cameras for a couple years that I get somewhat fewer missed focus shots with 7D than 50D, using same lenses for the same subjects and essentially using the cameras the same way. It really is optimized as an "AI Servo/Sports/Actioin" camera. Of course it can serve many purposes... the 7D's AF is much more configurable and has a whole bunch more AF points to work with. I really like Spot Focus, use it and Single Point the most. Occasionally Zone Focus and Expansion points come in handy.
I was surprised to hear about the 7D's special macro AI Servo focus mode, which samples subject distance 4X as often as usual when using any of the Canon USM macro lenses focused closely. It's not even mentioned in the manual, nor many other places. Combined with Spot Focus, this is might be a really useful tool for macro photography.
With my 7D, I've stopped using the one third ISO stops... I only use full stops: 100, 200, 400, 800, 1600... All the noise tests I've seen show that the one third stops (125, 250, 500, 1000, etc.) at best are only very slightly cleaner than the next higher full stop. The same tests show that the two third stops (160, 320, 640, 1250, etc.) are actually noisier than the next higher full stop.
With 7D and the other 18MP cameras, Canon recommends using higher shutter speeds.... There's a white paper on their website about the ultra densely packed sensors being more susceptible to camera shake. Where I used to use 100 and 200 ISO, I now set 200 and 400 by default, just to be sure I'm using slightly higher shutter speeds.
There was a lot of whining about "soft images" initially when 7D came out... partly due to the sensitivity to camera shake, but mostly because the camera uses such a strong anti-alias filter. I find I use a whole lot more sharpening on images than I needed with 50D (someone shooting JPEGs may not notice this, in-camera conversions might automatically apply more sharpening... But I wouldn't know, I almost exclusively shoot RAW).
7D is a real workhorse. It's the first really pro-oriented APS-C sensor camera that Canon has offered... and it was about time! I enjoyed earlier cameras, but Canon was late to giving their crop cameras all the respect they deserved! I think they've learned their lesson.
Have fun with your 7D... it's a great camera! (Not that the 50D was at all bad.)