Would need to know what you're wanting to do with it and what your budget is.
If it's to surf the web it looks good enough. If it's to game, I'd save up and do a forklift replacement of everything but the optical drives.
Currently I am just thinking about it, but the computer was supposed to last me until 2015 at minimum with some upgrades. I am just trying to figure out what to upgrade first. I do game a bit, lots of Civ5, TF2, Warframe, etc. and I also use it for some Graphics rendering (ProE).
Well... what is it not doing that you want it to do? Slow in games, slow to load web pages, etc?
If it's slow in general, an SSD will make about everything faster.
You could get a cheap aftermarket cooler ($25 Xigmatek Gaia) and overclock the CPU.
If the games are choppy a good entry level GPU is the Radeon 7770.
It is extremely fast for webpages and flash games and stuff, but my problem is, that overall, it is just a bit slower than what I am used to using at school... (Quad Core i7s are currently being used in my high school windows lab...) Overclocking has already been done a bit to 3.5Ghz, but my ram seems to be at full use all the time (as in speed), I saw that using speccy by piriform.
Games are good
Startup is slow
Outlook is extremely slow.