1. If you have switched, why did you switch?
I figured compiling everything must use a lot more electricity than installing binaries. See also Q3.
2. Do you still use Gentoo?
No, but I may go back.
3. What is your overall comparison of the 2?
(K)ubuntu had features I didn't know about. e.g. there are a few ways to get automounting going, and last I had tried, I didn't find any satisfying, so I was doing it by hand. Well Kubuntu/KDE4 does it rather slick. I'm sure Gentoo could do this too, but users have to find out about stuff like that and set it up themselves. I don't feel like spending my time seeing if useful new features are available.
HOWEVER, for some reason I can't get my ATI RV350 to use flgrx under ubuntu so 3D apps like SketchUp crawl, and my ipw2200 wireless driver always crashes within an hour in ubuntu. These two major drivers worked fine for me under Gentoo but not ubuntu, and since ubuntu tries to manage everything with minimal user input, I find troubleshooting more difficult than under Gentoo.
Oh and one more thing I'm reminded of by the obnoxious animated smilies aside this post. The Gentoo forums are fantastic, and generally have the answer to whatever you may be asking. Ubuntu, on the other hand, has several places the answer might be, since my kubuntu questions are often really ubuntu questions, and there's other derivatives too. Furthermore there seems to be a decent amount of misinformation on the ubuntu forums and seemingly very few people who really understand the problems and solutions.
4. Do you still recommend Gentoo?
Yes, whether or not I'm using it, I would recommend it to people who want to know how their computer works. Regardless of my distribution of choice, I think blanket recommendations are irresponsible.
5. How long have you used Gentoo?
3 years I think, on two laptops sequentially.