I have only seen the movie but I have heard a lot of discussion on the books and read articles on both sides because I was really fascinated by how popular it was and how everyone seemed to be quite passionate about whether it was abuse or sexy.
This is what I came up with:
No it's not an accurate portrayal of BDSM. Anyone who had that as their introduction do BDSM would definitely be very confused and wouldn't get what they expected if they decided to take that next step into any kind of fetish community. Christian is abusive and BDSM does not equal abuse.
No it's not garbage that's going to convince women that that is a healthy scenario. I'm turned on by the whole thing. Someone who wants to stalk you, own you, use you, abuse you. I like that. I'm also an adult who is perfectly capable of understanding that while that may be a fantasy I enjoy masturbating to it doesn't mean that I would ever tolerate such behavior in my real life.
So while I don't think it's an accurate portrayal and I do understand the concerns that people have I don't really think it deserves all of the heat it is given. It's erotica, it's porn, it's a fantasy. Fantasies, even fantasies of abusive behavior, are okay