I have the four post lift.  My biggest mistake was the 10' ceiling instead of 11'.  I can take my vette to the top but not most of my other cars.  Have to position it between the roof trusses(they are 10' apart).  As for moving the lift with casters, it is one handed without a car but this 6'3'' 225 boy can't move it with a vette on it.  I have the jack tray that I can move anywhere underneath to lift to remove wheels or suspension. It is also great for supporting the transmission or engine.  If I am just rotating tires or something it is just easier with a floor jack and jackstands.  We did not have the long winter so storage was not an issue but the original concept was to put the Vette and my '66 Mustang in the same amount of floor space.

I'm a jack and stand user at the moment but would love to have a four poster if I could afford it.  After all I do own a C3 and that gobbles up most of the cash.  Where to put it is the problem.  I could put it out in the open due to the weather in Oz being so nice all the time but then all the neighbours would want to use it as well.  I'll probably take the easy option like my neighbour and dig a pit with a drainage pump in it for when the wet season hits.....all three days a year when it rains.

Well, I'm with Ranger3 and Xfire for all the reasons mentioned above. Had the 2 post for almost 2 yrs. Wouldn't change even if I could. My only problem is shuffling vettes to get to the lift. ( I'm in heaven ).

I'm with aceinthehole and the other two guy's. It's alot easier to lift a little with a two post lift and work on you're back or from a seat  than to mess around with jacks and jack stands not to mention alot safer, although I'm a firm believer in doing what you have to do to get it done, but safety has always been an issue with me.