W G.

Pubby is one of the worst sites I have dealt with; if you are not happy with something and you offer suggestions that don't fit their way of doing things, they won't listen to your feedback and send you emails that are not pertinent to what you're trying to say. They won't listen to you. They will keep telling you they are the only review site compliant with Amazon (I wonder if I should ask Amazon this directly, as it is still a review-swapping site). They also always have to have the last word- paying customers are never right in their eyes; they are.
They charged me more than I needed to at the beginning—first, it was over $30 per month. Then, when I tried to leave, the site said, "Are you sure?" and offered a cheaper rate of $11. None of the support team offered me this, and I would have still been paying $30 had I not tried to leave. The cheaper rate enticed me to stay, but I wish I hadn't.
There are no incentives for authors to write decent reviews for each other with a reasonable word count (whether positive or negative, I might add), and you could find your book raked over the coals by some angry, wound-up grouch who decides to have a nasty old whinge about it that day—beware! There is constructive criticism and plain nastiness—trust me, you don't want the latter!
It is authors reviewing each other's work- essentially, many authors want to get swaps as quickly as possible to get as many reviews as possible, so this doesn't always guarantee quality reviews. One review I received just said 'Enjoyable'. Ha! I had just bought a book and given it a great review, and that was what I got when I used my snaps. Amazon removed it, too, of course.
I played the game as well as I could, always leaving well-thought-out and considerate reviews, but unfortunately, I didn't always receive that. I imagine someone reading this may think it is because I have bad books, but I am a graphic designer. I have contacts who are editors- I am incredibly fussy with my work and never put something out I am not 100% happy with, and I am sure it meets industry standards.
There are fabulous, genuine people on Pubby who are willing to write great reviews, but they are rare. I do not recommend this site (especially to headstrong authors who may want to challenge crap systems- you will be put in your place!), but if you are willing to risk it… good luck.