Other things that you can check out for yourself are:
1. Run a glissando (just use the tips of your 3 middle fingers) all the way from the bottom to the top of the keyboard and watch to see if all the keys come back up level with each other after you've played them. If they don't some work needs to be done on the action. You don't even have to depress the keys all the way to check this.
2. Open it up so you can see the inside, and check for rust on the strings. In general, does it look clean inside?
3. While you're in there, check the hammers. Is there evidence of moth damage? Are there deep "ruts" from where they hit the strings?
4. Also check the "bridle straps." They're those little leather thingies that pull the hammers away from the strings. It's really no big deal to replace them, but you probably don't want a whole bunch of them right off the bat! If there are keys that stick, sometimes that's the reason.
5. Check for broken or warped shafts on the hammers (the little dowel rod looking things.) Again, not a HUGE thing to fix, but who wants to start out with a bunch of stuff that needs to be fixed?
6. The big deal breaker would definitely be the sound board, and that's where having a technician look at it pays off.