No-one has really seen what DDR2-based Athlons perform like yet either. All indications are that they dont' get a significant boost, but still, they'll be on the market before intel. If I were going AMD, i'd surely get one of the new socketed ones as opposed to the older socket 939. But AMD are going with DDR3 in 2007/8 so I don't know if that requires yet a new socket or you can do a drop in upgrade to take advantage of a new core in Socket AM2. Or Move your Chip investment to a DDR3/AM2 type future platform, if such exists.
Either way, Core 2 is up by about 20 percent vs a similar current DDR1 based AMD chip, in the best case scenario. That's fairly large lead, even it it gets cut down, it'll still be a hell of a lot more competetive and aging Pentium line. Which themselves are not exactly slow. Hell most 2 Ghz + processors, with the exception of the Williamette, are not exactly slow. Pair any of them with a recent gen Gfx, and you'll always have a solid rig for many contemporary activities.