I have been on Effexor for over two months now. When I started it I was very bad. At the same time as it started to work, I was getting a new perspective on the whole thing, learning about dp and myself. I now feel a lot better, I haven't experienced extreme fear/dp for a while, and my anxiety has very much been reduced. I believe that the Effexor made this possible, gave my brain a chance to chill out and let me get on with life, letting my chemicals balance themselves out.
As for side effects/withdrawal. No drug is clean. Cipramil worked for me a year or so ago, then gave me a rough ride earlier this year, never experienced dp to that extent, and I stopped practically cold turkey. And started Effexor almost immediately. Things started to change almost immediately.
The side effects vary from person to person. I am not that bothered by physical sensations, and am able to disregard them. Some people are bothered by them, which will make you focus on them. This will be true for withdrawal aswell. Some side effects I have experienced are insomnia, overtiredness, increased appetite, er, lack of interest in what the birds and the bees do...,jerky muscle movements. These things just don't bother me, as I consider them to be easy to handle after dp. Jerky muscles is a bummer though, since i am a draughtsperson and can't hold a pencil or mouse still for too long...! oh and nightmares.
Some people may have more extreme reactions or even allergy to it so all you can do is give it a go. Withdrawal, if you have sorted out your 'problems' should be easier since a lot of 'withdrawal symptoms' are just the original problem coming back. There is a lot of bad media surrounding symptoms, but the way I look at it, if they are just physical it is less scary.
Cipramil made me feel worse mentally the last time I took it, the longer I took it and the higher the dose, the worse the dp. There is always a risk of this. I am quite drug sensitive - I am allergic to penicillin and have strong reactions to other antibiotics. Same with other meds, they either work extremely well or have adverse effects.
The side effects of Effexor are so minor to me that I would take it any day over dp. I don't feel like I've taken cocaine, though my confidence and sociability is better but that could be because I'm happier. For every person who has side effects, there will be a dozen more who it has worked for. Why make a song and dance about something that's been plain sailing? You only hear the bad stories. Had this very conversation with a very nice doctor today!
Hope this has helped - its your call!