I have both 2 cd sets of the Glimpses comps. Not great sound on hand, and Glimpses 3 and 4 especially sounds purty muddy at times. Not as bad as the job they did on the Texas Flashbacks box, though, or on the "Pilot" label (probably connected to P&P, Radioactive, etc) reissue of the Other Half LP where the crowd noise at the end of track one just kinda stops for a minute before picking back up lol.
I know that there is likely to be a lot of people on this board who dislike P&P and their "affiliated" labels, and I get the rationale for this feeling and share it to a large extent. That said, I like the ability to pick up boots of "historically relevant" comps (also usually boots) for cheap (I paid $20 for the 6 cds in the Texas Flashbacks box, and most of their CDs are available through the bargain discount dealers like red tag market, etc.).
I say go for it, if you can find 'em cheap enough. But, y'know 'buyer beware" and all that.