Which operating system

[Medallion]

I am running OS X Snow Leopard on my 2008 iMac.

I've been told this a good system to run, however would like to upgrade to ideally Mountain Lion.

However is it worth this upgrade? I don't want to sacrifice performance.

 

[BeamWalker]

If you have 4Gigs of RAM or more I don't see a problem running the latest OS X on an iMac 2008.

 

[JustMartin]

I'm running Mavericks on my mid 2007 with 4 gig of ram and it's not too bad.

 

[PixelpusherBV]

As JustMartin, I too am running Yosemite on a mid 2007 iMac with 4gb ram and it's running surprisingly sweetly. Upgrade to Yosemite, you should be pleased.