It's been having issues since the release of version 22. Right now I'm using 18.104.22.168201091635 with Indigo, and it seem to take forever to process a test result set. A test that take 2 minutes to complete on force.com would take more than 15 minutes to parse, during which the whole Eclipse "Not responding" with the eclipse.exe thread running full throttle.
It's not an issue with Indigo, because Helios gave me the same results. It actually used to be even worse with some versions of v22, which would die during the parsing process.
Before version 22 (Winter '12), things used to be just fine. I'm not on a high powered computer, but routine uses never gave me trouble back then.