I'm considering an upgrade to postgres 8.4.x

I'm on 8.3.10, but I like to keep up to date and take advantage of performance improvements.

I've seen mention in a thread that the latest PT3 beta (I'm on 3.07.2) can take advantage of some features in 8.4.x; but it also looks like the migration can be a bit of a pain (backup/restore required)

So, my question is: what are the known benefits of being on 8.4? What does it gain you within PT3? I'd like something to give me an idea of whether an upgrade is worthwhile...

The performance improvements aren't all that large, they come mostly from the change in how checkpoint segments are planned if I recall correctly. If you're not doing heavy datamining or cache rebuilding it's not going to make any noticeable difference.