* Me personally, I love i7's just because there sexy and beasty
* They also offer tri channel ram and out perform AMD in every way to my knowledge
* Huge company, so they have great customer support for problems
It is hard to over generalize. Since I switched from Apple II's to PC's, I had always used Intel, with the exception of a Cyrix computer in mid 90's (big mistake).
However, in my last computer, I was set on an i5-750, but looking to i7-930 (because of multi-threading), as I do a lot of video encoding. Right before I pulled the trigger on my new system, the AMD hexacores came out, and I ended up getting a Phenom IIx6 1090t.
It does very good in video encoding, and has great benchmarks in Handbrake, which is my favorite encoding program (along with XVID4PSP).
So you should take into account what your needs are and buy what you are comfortable with.
Low to mid-range gaming, AMD
Everything else, Intel
I look at very specific usage on a case-by-case basis. For instance, I was building a new web development server and NAS and I just didn't need any more power than a Athlon II X2, however I wanted to go Mini-ITX with it - the cost of a AM3 Mini-ITX board with SODIMMS actually took the price a good chunk higher than a i3 540 build.
I have more CPU than I need, but overall it was cheaper.