Downsides: I have no idea where I'd wear it. The straps are too long and would need to be taken in. It's just on the verge of being too big -- it looks great right now, except I really want to lose weight and if I did then the whole dress would probably need taking in. Also, I think I'd have even more "support" issues (trying to find a bra) with it than I already have with the (lovely but challenging) halter dress I got last year.
I don't think I have anywhere "appropriate" to wear it. I mean I could wear it to con, but it's the kind of dress crying out for a fancy ball to wear it to. I'm not sure I'd be brave enough to wear it to the kind of dressy-but-not-elaborate events I do sometimes go to, like weddings. It's not a "stealth" dress, that's for sure. Also I'm cheap, and $85 is a lot to spend on a dress to keep in my closet.
On the other hand, I really like it. I felt glamorous wearing it, and my girlfriends all loved it also. I put it on hold for 24 hours. (I should have gotten a camera-phone pic. Why did I only think of that now?) Now I don't know what to do!
[edit: I bought the dress. (:
Oh and it had been moved from the 40% off rack to the 50% off rack, so it was only $76 - including tax!]