IMHO its not worth it if you need to buy a SATA controller, unless you really need to have the fastest drives around: the WD Raptors only come in a SATA version. They are expensive and relatively small though.
SATA does have some advantages: longer, more flexible cables for example. In the future SATA drives may be hot-swappable and capable of command-queueing. SATA drives are only a little more expensive than equivalent IDE drives.
At this time buy whatever is convenient. There is no real need to buy SATA (unless you want those Raptors). The future will most likely be SATA, but current IDE drives will do perfectly well for a couple of years.