Here's what it can't do. It can't simply be loaded and run. Values must be customized to get real use out of the mod. Values must also be tracked and updated when game mechanics are changed in patches. Thus, it's not for the truly casual player. It's also not for the truly hardcore player because calculator spreadsheets like Rawr still (based on my reading) provide better itemization. It also doesn't take into account the "intangibles" of an item like survivability stats for a DPSer. Finally it can't calculate the value of flavor text, use activation or set bonuses. You still have to consider these things for yourself.
That sounds like a lot of things it can't do. Trust me, it's still awesome. If your math (or someone elses math) is valid then it will protect you from the "oh that looks cool" need roll that everyone hates. It will also keep you from piecing together the wrong gear, crafting downgrades or buying junk on the Auction House. (We've all done it.)
Now, there are two ways to put together Pawn values. Option one is to do your own math and then manually enter each stat. That's great if you're a mathematician or a stat-junky. I've actually been accused of being both, but I'm too lazy. Enter option two: Find someone else to do the work for you. The great thing about option 2 is that people are nice enough to put the values in an easy cut-n-paste format. Here's some that I've found.
Hunter DPS direct from the Hunter DPS Spreadsheet v80 on Elitist Jerks.
( Pawn: v1: "Hunter": ArmorPenetration=0.323, RedSocket=9.204, CritRating=0.373, Intellect=0.937, MetaSocket=12.08, Agility=0.575, HasteRating=0.258, BlueSocket=4.045, YellowSocket=8.648, Rap=0.369, HitRating=0.506, Ap=0.369, Mp5=0.432 )
Feral Druid values compiled by Flyv.
( Pawn: v1: "Cat (Toskk)": ArmorPenetration=1.0161, RedSocket=37.312, FeralAp=1, ColorlessSocket=37.312, Strength=2.332, MetaSocket=103.21, HasteRating=0.7236, Agility=1.6992, ExpertiseRating=1.0362, BlueSocket=18.66, YellowSocket=26.92, CritRating=0.83, HitRating=1.0334, Ap=1 )
( Pawn: v1: "Bear (Toskk)": RedSocket=113.7, ExpertiseRating=1.306, DodgeRating=2.685, ColorlessSocket=172.4, MetaSocket=329, Agility=3.429, Health=0.411, BlueSocket=172.4, YellowSocket=101.3, DefenseRating=1.885, Armor=1.066, Stamina=7.185 )
Now keep in mind that Flyv & the folks over at Elitist Jerks will all say that gear ranking is an ongoing process. These numbers may not always be the best ones. Theorycraft changes. Patches get released.
I plan to keep searching for good sources for not just my characters but toons played by all my friends and post them here.