I'd been using Lightroom, which felt like it was running through treacle, for some time. I thought I'd have a go at making the machine run quicker, and simplify my three data volumes down to one, so I striped the three 470-gig drives yesterday (leaving the 10K-spinny 160 gig as the system drive), and it's like a new machine. Very impressed. Lightroom is now usable; almost fluid in its usability.
The downside is I'm now essentially three times as likely to suffer a disc failure as if I had one huge drive the same size, but I've got good backups, and the performance increase is worth it.