I've put together a 4 post before without any problems.
having said that, when I get my two post for my own garage, I'll be paying a professional to deal with delivery and installation. for $400-500bucks, it's worth it to me.
here's something that I don't think has been mentioned:
you will probably never need to use it if you buy a quality lift, but you may void your warranty if you don't have a manufacturer authorized installer put your lift together. I believe that this is the case with rotary.
I did find a local company that was "off the record" willing to let me put the lift together and then they would come buy and inspect it and "sign off" on the install, thus allowing me to maintain my warranty status.
again for $450, it's not worth the trouble to me.
-chris