Since buying my iMac in 2007, I've never once done any form of maintenance with regards to files, permissions, etc. That's right, nothing. I use my iMac not only as my personal computer, doing the usual internet and email, but also as my all-purpose machine where I do programming for websites. I also run the excellent VMWare Fusion product to experiment with different operating systems using virtualisation. 5 years of neglect constant use without maintenance has made my beautiful machine feel like it is somewhat struggling at times. Following the usual maintenance of disk space clean-up, file system permissions and so on, I decided to bit the bullet and re-install OS X. After backing up everything to an external hard drive and dropbox, I've performed the following so far (and yes, my machine really is THAT old to warrant starting from such an early version of OS X):

• Installed Tiger, erasing the current disk partition. I have a bootcamp partition in place for using Windows 7 and Visual Studio for asp.net stuff, so I've left that alone.
• Installed the Leopard upgrade drop-in that came shipped with my iMac.
• Installed Snow Leopard (in my opinion one of the best OS X releases ever).
• Installed only the latest Snow Leopard combo update to gain access to the Mac App Store application.
• Re-downloaded my previously purchased copy of Lion and ran the installer.

All good so far. Until I cam to purchase and install Mountain Lion. My iMac is listed on the list of supported Mac's, and I've heard great things about Mountain Lion improving the performance compared to Lion. Unfortunately my download stopped at the 54 Mb mark last night. Tonight I'll be clearing the Mac App Store application cache and re-attempting the download again. I'll report back if the performance improves, but hopefully a combo of the latest OS X as a fresh install on a re-formatted disk partition can put me off upgrading a little longer...