Dungeon magazine is the best buy for the money right now, especially if you are a subscriber. Dragon comes in second place, with not as many useful tools for the time-crunched DM, but lots of great ideas for a DM with free time to incorporate them into his campaign. I also agree with the OP that the Dungeon tiles give a great bang for the buck. Dollar for dollar, it is probably one of the most valuable WotC products ever released.
I also happen to think WotC adventures are high quality products for the price. Think about this: if you buy Complete Psionic, even if you play a heavy psionic campaign, you might use about 10-15% of the content over the next year. However, if you run an adventure, you end up using 85-100% of the content (depending on how thorough your players are). That is serious bang for the buck right there. I buy every single WotC adventure published (of course I buy all WotC stuff, but I buy adventures from other companies too for this reason).