I currently use Poker Office. That being said, I let it display VP$IP, PFR and agression factor. (and amount of hands I have on said player, to see how accurate it is)

Preliminary results:
VP$IP: over 50% means they're a donk usually. Possible calling station. If it's really low, like below 20%, they're a nit. Note this is 6max I am talking about, it might vary in 10max. Somewhere between 25-40% means they could be a decent player.

PFR: This doesn't say as much about the player as VP$IP imo. It just gives you an idea about the respect you should have for their raises. The range you can put them on, so to speak. If their PFR is 3.1% or something, they're really only raising their monsters (AA/KK/QQ/AK). If it's 25%, then they're raising one out of every 4 hands.. so their range is huge.

postflop aggression factor: Sadly, I haven't been to get any useful information on a player based on this. Whether it's high or low, dunno, I haven't seen any strong correlation with their playstyle or skill level, or any useful predictive elements. You'd think that a higher aggression factor would mean they c-bet or bluff more, but this isn't consistent with my experience at all. If anyone has been able to use this parameter in a useful way, I'd be more than happy to hear about it!

I have now added Flop-Turn%.. I'm going to see if this adds some predictive value about my opponents. I'm mainly looking to see if it can be used to single out calling stations better. (which I would expect to have a high % here)