Apart from the ton of features and excellent stability, the board doesn't offer any spectacular performance and is far more expensive than the competition, or even other Asus boards. You'd be far better off investing in anything DDR2, rather than forcing yourself down and extremely expensive upgrade path. It will allow some future proofing, but by that time in 12-18 months, you might as well upgrade the motherboard with a newer chipset which will undoubtedly support faster DDR3 modules and newer features as well.
It's a really weird situation because it's genuinely a really good board, but there's absolutely no reason to buy it. Get the P5K Deluxe or something P965 or nForce 680i (LT) SLI instead... oh and a ton of performance DDR2, a large monitor, a better graphics card and perhaps a new car or apartment as well. You know, the same kind of money you would have spent on the P5K3 Deluxe and DDR3.
It you're after CrossFire support to match a couple of Radeon HD 2900 XTs you've just bought (I'm assuming you run Vista here) and are dying for an updated chipset rather than the antique 975X, then you've either got to settle for the DFI LANParty UT ICFX3200 T2R/G, or wait until September for X38. However, X38 will also be DDR3, sooo I'd just buy the DFI...
Source:Asus P5K3 Deluxe WiFi AP with DDR3