I asked at the Apple store when I bought iLife '08. According to them,(Indianapolis area) web galleries will not work without iPhoto '08 as far as uploading goes. However, anyone can view your web gallery once posted (PC, Mac, whatever). Pretty lame if you ask me.
Hope that helps, if you have any other specific questions I can try to answer them. I uploaded a set of pics last night to check, works pretty nicely. Very fast to upload and very easy to do. I'd say 5 minutes for the whole process with the software update for iPhoto '08 included in that time frame.
The Web Galleries are pretty cool. Probably the nicest and simplest hosting I've worked with.