I just upgraded to the latest Ivy Bridge. I pretty happy with it. Multi tasking seems much smoother now things seem to load up just hair faster. Haven't had a chance to fire up a game yet since it was late by the time I finished. I only upgraded the CPU, Motherboard and Ram. Specs listed below.
I had Intel Core 2 duo Conroe 3.0g, 4G Ram, and ASUS P5n-e Sli MB. And now have I5 3570K, G.Skill 8G ram, ASUS P8Z77 MB. The new mother board has all kinds of overclocking features, which I haven't tried. But I'm not really into overclocking so I probably won't mess with that.
I'll definitely get an SSD in the future. I didn't really have any issues just plugging in my hdd with the existing Win7 install, it did seem to mess up my Nvidia driver and Norton AV and some other not that important programs. But just reinstalled those and all is good. I thought I was going to have to do repair install, but I was able to just load all the new drivers and activate windows. Overall went smooth.
One issue I had, that was I neglected to check if it had IDE connections, and it does not. So I had to do away with my Win XP drive and one of my optical drives. No big deal though since I almost never ran the xp anymore and the optical drive was just a hold over from other pc builds.