I just did the exact same thing. Replaced my s939 X2 4200 system with a core i7, keeping it in the P180. I had to pull the lower-middle fan out because I switched to a longer, modular PSU and it wouldn't work with it still in there. I still have no idea why it took them all the way till the P183 to move that fan in front of the hard drives, and it wasn't' like that at the beginning.
Still, it's still a fine case. The revisions that they made in the 182 and now 183 are definitely a step up, but not critical. I'm planning on getting myself a new case come the new year when I get a new graphics card and HDD as well, but mostly because I also plan on putting the s939 back together in the current case to run as a server. If you're budget constrained, keeping the P180 around is perfectly acceptable.
Intel i7 860, Asus P7P55D Pro, 4x2GB Corsair XMS3 1600 (CMX4GX3M2A1600C9), EVGA GTX 560 Ti Superclocked
Seagate 7200.7 160GB, WD Caviar Black 640GB, WD Caviar Green 1TB, WD Caviar Green 2TB
Dell 2408WFP and Dell 2407WFP-HC for dual-24" goodness