I didn't use them last year - this season will be my first. But I would advise anyone to check out the sample league and if it seems like a potential fit for you then setup a league and walk through all the settings, including asking any questions if you have any - their responses are timely. Then simply compare it to others you are considering. You may find sites with more features and you may find sites that are cheaper, but for me they are my clear top choice because the overall package is the most cost-effective for what we need.
One feature I particularly like is their FAAB system. Quite flexible as far as entering contingency bids (way better than CBS). But what makes it particularly nice for us is that we can include our waiver bids with FAAB bids and mix contingencies as follows:
1st Priority: Waiver claim Jones, drop Smith
2nd Priority: Bid $12 on Harrison, drop Smith
3rd Priority: Waiver claim Ramirez, drop Smith
4th Priority: Bid $13 on Martin, drop Smith