Buying MacBook Pro off of craigslist - what to look for?
I wouldn't purchase this machine unless it's still covered by AppleCare.

Inspect it closely for nicks and dents, indicating a drop.  I would check the Console logs for any indication of ongoing OS level problems.

Unfortunately testing hardware can take a while, but is worthwhile before buying.  Run AHT (see http://support.apple.com/kb/HT1509?viewlocale=en_US&amp;locale=en_US) and do the quick test.  To do it you'll probably need the original disks that came with the machine.

The only other thing I can think of would be to verify that modules such as bluetooth, WiFi, Ethernet etc, are showing up properly (and information is being populated in) system profiler.  To get there, hold option while going to the apple menu - it's the first option.

Listen for loud fans, can indicate overheating or bad sensors.

Aside from that... it's always risky.  Check Apple's stock of refurb units.  They come to you refurbished by Apple, with a 1-year warranty, and often don't cost that much more than a CL unit, but with much less risk.