How do you use statistics (PT, GT+, Playerview) to make decisions?

[Withen]

I've been using pokertracker pretty much since I started playing three months ago, and recently started using GameTime+. These programs have helped me significantly, but I really feel like I could be getting more out of them. I'm specifically interested in what statistics people look at, and concrete examples of the decisions that those statistics influence. Let me give you some examples.

I play at Party 2/4, so things may be different at higher/lower limits - I am still interested in how use use statistics at different limits, though, as I do plan on moving up (some day).

VPIP
If someone has an extremely low VPIP (<10), I narrow the range of cards that they could be holding (less likely to have garbage hands). If someone has an extremely high VPIP (> 30), I widen the range of hands that they could be holding. The higher the VPIP (40, 50, etc), the more possible hands they could be playing with. In a more general sense, I use this statistic to gauge the ability of my opponents (I realize that this is not the primary factor that dictates skill, or even necessarily the most important.. but it is the easiest to quickly look at, and usually is a good indicator).

PFR
If someone's PFR is extremely low (0-3), and I have a good number of hands on them (100+), I will be much more likely to throw away my hand preflop against a raise. The likelyhood of the raiser having AA, KK, QQ, or AK with such a low PFR seems high. Conversely, a player with an extremely high PFR (20+) is someone who I am more likely to try to reraise and isolate, or perhaps call a hand I might not normally call with.

AF
AF tells me how much I should be respecting bets and raises postflop, and sometimes lets me know what players I can count on to help me check-raise.

Thats pretty much all I look at (right now). A few questions I wouldn't mind having answered is:
How many hands do you need on a player before you can consider their statistics somewhat reliable?
How do you use per-street aggression factors?
How do you use statistics like W$WSF, WSD%, and W$SD? What other statistics are important to consider?

Thanks in advance for your comments.