The customer support, hands down. You basically never have to wait on hold, either.
These people actually care, and they will help you solve problems step-by-step. They are very friendly, VERY knowledgable, and among the best customer support providers I have ever encountered.
If the service providers can't solve the issue right on the spot, they will figure out a solution in a timely manner and send you an email or call you back. If they email, it's always super well done and step-by-step...often times with screenshots.
They don't technically provide any accounting advice or even book keeping advice, but they provide all the advice that they possibly can without breaking any laws...and it;'s super helpful because I often feel like I'd be helpless without them, or I'd have to pay a consultant some good money to get what I need answered. They are like a team of consultants who know current laws quite well and understand the accounting process very well.
A+ customer service
The system interface makes sense, but it is unattractive and rather clunky. That being said, the interface is probably an acquired taste as I find myself liking it the more I become comfortable and efficient with it.
It does take a lot of memorization, though, and the searching algorithm isn't strong (making it hard to find stuff if you don't already know where to find it and can't find it under where your best couple guesses lead you to)
Get it, do the training, spend at least an hour every few days on it, and you will become comfortable with it.
Providing a complete accounting system, transaction processing system, as well as agent record management system.