I've been a customer of theirs for a few years now. I have used them off and on over the years but have used them every day the last couple of months.
I have to say, they are a very underrated book.
Customer service is competent and friendly. They use common sense if you have any issues. You can actually call these people and talk to a human unlike some other books. If you message them, they will usually call you back or at least answer you via email in a reasonable amount of time.
They grade wagers really quick.
Deposits credited quickly. Great bonus offers if you qualify.
Payouts are just as fast as Heritage (same day, usually in the afternoon).
They offer some nice contests with a lot less competition as the major books.
If you are a bonus taker, I encourage you to give them a try. If you are not a bonus taker, probably not your type of book as they don't have low juice (they have standard including dime lines on baseball).
I guess it all depends on what you are looking for in a book and what type of player you are.
Overall, I'd rate them as an A-