I was doing a little research today and collected some interesting stats.  According to what I've found, it should be easy to direct your customers to better sports books.

Bwin Ratings

SBR rating C-
http://www.sportsbookreview.com/sbr/bwin/

SoccerBetting.info - 42 (out of 60)
http://www.soccerbetting.info/bwin.php

Top 100 Bookmakers - 2 (out of 5)
http://www.top100bookmakers.com/bookies_bwin.php

Surwins.net - Average Visitor Rating: 3.5 (out of 5)
http://surewins.net/bwin/bwin.htm

Bookmakers review - 2
http://www.bookmakersreview.com/Sportsbooks_Ratings_sorted_alphabetically/
2 Poor. Assigned to bookmakers regarded as having significant weaknesses which could negatively impact a player's betting experience. In some cases these weaknesses are magnified by the unwillingness of the bookmaker to correct past problems or to change business direction over the long term. In short, if you happen to play with bookmakers rated 2, you are probably asking yourself for trouble.

Goonersguide.com - not listed