Focusing on the bad guys was definitely a fun and rewarding choice for Salvatore.
Yes, he's softening them up a bit, and in this book, we get a good glimpse at the distant pasts of Jarlaxle and Entreri, something that Salvatore's only obliquely hinted at before.
The plot of this book is unusual -- it's almost 3 short stories. Not a bad thing, it breaks up the rhythm and expectations, which is totally cool.
We get a measure of redemption for the main characters, but not in a way that ruins or fundamentally changes the characters.
I sincerely hope that he's got more of these books in him. I can also see how these bad guys will run into Drizzt and our heroes later, and probably team up. Not a bad thing, either.
Super fun. After I've invested this much (21 books, by my count, I think it's TOTALLY WORTH IT just to get to these books here. Again, start at "Homeland" (Salvatore's wikipedia page provides a good order), but perservere. Get here. it's awesome.