A $200 I7 or i5-860 is indeed a great deal but they're normally $300 CPUs, the i5-750 is its current competitor and weighing everything up I just have to side with the AMD chip every time. Simply having a recognised upgrade path could be enough to swing things imo. That's an area where Intel have really dropped the ball.
Oh, and you're right I shouldn't have left out the higher TDP. It wouldn't sway me but a 125w CPU is pretty difficult to class as "mainstream".
Its hard to judge really, as we're going future software trends, but I think I just prefer to err on the side of "buy the most cores your money will get you" as honestly, any 3ghz quad core CPU is more than enough for today's software and in the past this route has always seemed the best option. Anyone who bought a Q6600 instead of an E8400 back when many sites were pushing gamers to the latter can attest to this.
Now if only these AMD chips offered hyper threading.............
I should probably clarify I'm not biggest fan of the $300 variant, I think Intel may just have better options at that pricepoint but that $200 chip, damn, that things priced to fly off the shelves. My argument of course would be that most are set with that $200 chip and if you want more performance then aim for the upcoming "mainstream" 12 thread i7-970, it'll be a big leap in price , sure, but its the next big breakthrough in performance and it definitely justifies a price premium. I don't think anything below it really offer enough to justify the expense over AMD's new $200 hexa core, personally.