In another thread, someone linked a review of Western Digital's drive, and it did okay, but not spectacular.

That was a pre-production model, it seems they have improved quite a lot since then.
From storagereview.com :

Our preview noted the following:

Many readers may be disappointed with the Raptor's relatively lackluster desktop performance. For various reasons, enthusiasts view an increased spindle speed as the largest factor in single-user performance. The reality, however, is that desktop usage predominately consists of highly-localized patterns and is affected more by caching strategies than marginal mechanical improvements. Western Digital's JB series may very well continue to stand as the premiere choice for those seeking the ultimate in single-user speed.

We're more concerned with the Raptor's server performance. While it is definitely a step above standard 7200 RPM ATA drives, the beta Raptor trails today's 10k RPM SCSI drives by substantial margins. If WD and SATA are to have a chance at cracking the enterprise market, the Raptor's multi-user performance must approach the levels delivered by Cheetahs and Atlases.

In the end, ironically, the Raptor is a world-class desktop unit and a decent but unspectacular server performer. As we have already remarked, the Raptor's server performance falls somewhere between that of a 10k SCSI drive and 7200 RPM ATA units. It can admirably fill the niche formerly served by the defunct 7200 RPM SCSI segment. To have a shot at higher-end multi-user applications, however, future Raptors will have to incorporate command queuing, a feature that allows SCSI drives to scale well beyond the Raptor's showing as I/O depths become heavier.

WD's drive, however, delivers single-user performance that matches and even exceeds not only 10k RPM SCSI but also that of 15k RPM units. It is the answer to many years of prayers from power-users and enthusiasts worldwide