Even though short term stats may not give you the best overall read on a player, it will tell you how he/she is playing in the current session (and that is 1/2 the battle!). Stats combined with your personal observations of how they play should give you a pretty good read.

Example, you only have 30 hand on someone who has a VPIP of 50% and when you see his showdowns and other types of play and he calls down all the way vs aggro. with J8o, 98s, etc. I feel confident categoring him as a loose/passive.

I pretty much use bison's rules for rating players with some customization in my HUD. This is what I use for full-ring VPIP in my HUD:

ORANGE: 0 - 14.99 - Too Tight, may be rockish.
RED: 15-19.99 - Possible Tight/Good (depending on PFR)
YELLOW: 20-29.99 Loose
GREEN: 30-100 Here fishy, fishy!