Have a Mac Mini I bought 3 years ago, never upgraded to snow leopard, installed Parallels 3, an early version, and every time I got an upgrade from Apple for OSX installed it slowed down Parallels. Upgraded several times to new releases of Parallels and again, every time Apple gave me an OSX upgrade Parallels performance disintegrated. Finally it got so bad it took 4 minutes to boot XP and about 5 minutes to start up Quickbooks - became totally unusable. Parallels support people kept trying to help me and kept going over the same solutions I tried before, from different people who did not seem to communicate with each other. Didn't have the hundreds of hours of time it would take to work with all these people so I just got an old XP laptop going again. Today I got my new Macbook Pro and will try Fusion.