Dropbox is a pretty nice replacement for iDisk but replacing the Gallery was a big pain. I tried a bunch of different services and finally settled on www.dphoto.com because it has the easiest setup to get a clean looking gallery that rivals MobileMe Gallery. It's not too expensive either ($30/$60/$90/year), here is my coupon code for a 10% discount: D92731DE
The only real downside is that it is completely Flash based, but they are working on moving it over to HTML5 instead. The iPhone version of the gallery is really nice though (not Flash). They also have export plugins for Aperture and iPhoto (found here: http://www.dphoto.com/#/news/) and there is a 30 day free trial.
Try it out and see what you think. Best of luck!
-I ended up turning off PhotoStream because it slows down everything and really has no added benefit. You still have to copy the photos to your hard drive to save them. What a shame that Apple murdered off the one really killer feature that I used.