Among those really into bdsm the series is widely scorned- with a mix of envy for the author's millions. (I haven't read them, but it makes me think highly of Grace, Spikebaby, EW, and Vetruviun, etc... because they share the same opinion as many I trust.)
I admit to reading the "beauty" books years ago- they were a little over-the-top too (remember when she essentially pooped gold dabloons)
If you're looking for better quality erotica, I suggest literotica.com it's amateur, but free (look up the top BDSM/exhibitionism/whatever your interest/etc stories in the last 12 months)
http://www.literotica.com/top/)
There's also been an explosion in the last few years of semi-pro writing of erotica on sites like smashwords and amazon that's a bit kinkier than typical Harlequin romances. For example, if you're into spanking, for a couple of bucks you can read something better and hotter than FSOG at sites like this...
http://www.stormynightpublications.com/
Frankly, I'm a huge fan of 50 Shades... it was an introduction to kinky sex and a key to unlocking a hidden desire to get tied up and spanked for millions of horny housewives. I'm just hoping I can fulfill that for a few of them!