Eiffergan,
I've had my 55 on caster for about two years, on both hardwood floors and tile floors, and I have never had a single problem. Not sure why you re getting lit up here...
I did it because the stand was not quite high enough for my liking, and the casters raised it up very simply. If I were to move it, i would definately drain alot of the water, but I don't think it would be any trouble to move after that.
As for the whole weight distribution thing, I don;t agree with what is said here. The weight is sent down from the tank to the bottom of the stand by the corner and center braces. I placed a caster under each brace, so basically the weight is distributed directly to the caster through the brace. It may actually be more efficent (assuming that both the brace and the caster can handle the weight - which they can). Theoretically, the additiona fo the casters should not affect how the weight of the tank is ditributed down through the stand, rather oit only affects how the stand distributes the weight to the floor. Again, as long as everything can handle it, I think you will fine, and a 2X redundancy is pretty good.
Stewart