Out of the ones I've tried, 5-MeO-AMT, 5-MeO-DMT, and 5-MeO-DiPT were pretty bad. I guess 5-MeO-DMT is probably worth trying, as some people seem to get a cosmic bliss thing going on. It was like smoking pure terror to me though. 5-MeO-AMT just felt wrong in every way possible. 5-MeO-DiPT has a pretty neat tactile enhancement effect; it felt like I could feel each of the individual ridges of my fingerprint in extreme detail as I ran my fingers over objects. Other than that it was awful; nausea, jaw clenching, anxiety, the twitches, etc.
The DOx series gets a bad rap, IMO. I've known people that had bad acid trips and assume they must have taken DOB or something. I didn't like DOI. It made me very uncomfortable and nervous the entire time. DOB was ok, but could take it or leave it, and would not want a large dose. DOC and DOM were great, though I wish they lasted about half or 2/3 as long as they do.
2C-I is the crappiest of the 2C-x chemicals I've tried. I used it at doses from 12-25mg or so, and all it did was give me a headache and a sort of mental fog like I'd get from smoking too much poor quality cannabis (or rather, the feeling a few hours after doing so). Other people around me got completely fried on it and had a good time though. I'm not sure what the deal was with that.
2C-T-2 caused too much nausea to enjoy. It just wouldn't pass. I don't mind all that much if it is something that will go away after a while, but this just didn't let up until it was over. That puts a damper on everything for me.
DXM is definitely the busted up hoopty of the dissociatives. It works, and fairly well... but I'm seriously afflicted with very unpleasant hangover effects all they next day (too messed up to do anything), and then feel weird the 2nd day. Ketamine and nitrous blow it away; haven't had the chance to sample PCP.