I found this as part of a review of their card grading service . . . very telling:
"Word on the street:
I haven't ever heard of PGS prior to researching this piece. However, I did a little research on eBay to get an idea of market demand for PGS graded cards. I did a search on completed auctions and found a 1990 Fleer Sammy Sosa PGS card which closed at just over $18.00. Then I found a 1990 Fleer Sammy Sosa PSA 10 card which closed on the same day at over $100.00. If you are ever considering the purchase of one of these off-brand grading companies products as an investment, this is an excellent research method to determine market acceptance compared to the "Big 3".

Also

PGS will auction off your graded cards on eBay for you at $2.00 + 5% commission a pop.

Yes that is correct . . . the grading company will sell your graded material on ebay and take a percentage of the final sale price . . . Thus this independent third party grading service actually makes more money by overgrading your card/coin/chip.

The PGS website tells us:
All of our grading staff have many years experience in item collecting and have been trained to grade to PGS standards.

Again this is hits a key point, PGS grades to PGS standards, apparently its easier then grading independent standards, and since they set their own standard they can never be wrong.

But unlike the last guys to try this, they don't even pretend to have a warranty:

Grading involves individual judgments that are subjective and require the exercise of professional opinion which can change from time to time. Therefore, PGS makes no guarantee or representation and shall have no liability whatsoever to the customer for the grade assigned by PGS to any item. [\red]

then they contradict themselves with a warranty limited to return of fee paid

PGS's liability for errors in labeling and/or grading is limited to PGS's charges for grading only.

But at least they sort of admit that there ridiculous service has no bearing on value

PGS makes no warranty expressed or implied in regards to value of items after grading.