Should I pay $50 for a positive App review?
jasonlbaptiste: a) is it disclosed?  If it's disclosed as a sort of paid advertisement, then it's okay.  It's more of an ad, than a review.
b) what's their traffic?  See if there really is a "backlog of apps to review".  
c) Be concerned that they will only publish it if it's a positive review.  That means they're only doing this if it's favorable.  
d) What other apps are there?  If it's third rate apps that look like they can only get a positive review if paid, then id abandon it.Everyone is going to have their own opinion on this.  No one is right or wrong, this is just my point of view.  I hope it helps.