As far as importing wii's and connecting them to the net, there hasn't been any issues and thus your regional settings will be for an NTSC console you'll get the NTSC updates rather than PAL ones, or so i assume, i'll have to ask a couple folk about that.
IF you do indeed mod an aussie cnsole you will be able to play NTSC games, just that your TV will need to support NTSC input (majority of TVs do anyway), though i believe you cant directly update the wii via its update program when they come out as with the likely possibility of bricking your system which is irreversible, thuogh there is a workaround for that anyhow
Advantage of being connected to the net will allow you to play Wi-fi connection based games, though at current there isn't that many, only Mario Strikers Charged, Pokemon Battle Revolution and Guitar Hero 3 that have that at current, there could be another 1 or 2 out there.
Also you can add friend codes from your friends wii's and send them messages and Mii characters to each other . Then there is the Wii Shopping Channel which allows you to download the Internet channel (web browsing) Everybody Votes, Mii contest channel and downloading of Virtual Console games (from NES, SNES and Turbografx to N64 and sega megadrive).
Plus being able to do system updates as well