After my little Lego set binge the past couple of weeks I think I'll wait until this fall or maybe Christmas for another. But I'll save up for a bigger set - Death Star, probably. I actually prefer the SSD as a display piece but I also know having something to play with will be fun and my daughter will much prefer having a bunch of minifigs.
It'll also give me some time to keep an eye out for any sales. My best bet will likely be a 20% off sale at Toys R Us, which will bring it to $400. We will have a Lego store opening here this summer but even with double VIP points that still only knocks $50 off the $500 price, and it's not an immediate deal either as I still have to spend them.
edit - just got thinking about this after seeing you guys talk about the tower bridge. That one isn't on my shortlist, though, I hate cheese slopes so, so much, so that set would be horrible for me (even the 28 odd ones on the sonic boom annoyed me a little).