I haven't head any dealings with them, but it seems easy enough to check. Their authors are listed on the main page so you can track them down and ask some probing questions to see if they're happy with their representation -- I saw some big names.
For me, there's only one big red flag. The director also does writing courses which are advertised on the site. A reliable agent rarely has time for such things, but even if they do, it's a conflict of interest to mix the two.