"Main" computer can be a vague term, especially for someone who has several.
I voted "yes", but with some caveats.
If by "main" computer you mean the primary system I use to access email and the web, that'd be my iPad.
If I add Quicken, FTP, DVD Profiler, and a couple of other "every day" apps that I use, then yes, that is NOW my brand spanking new MBA.
If to that I add hard core gaming, then no, my Dell XPS 720H2C remains my "main" computer running Windows 7 Pro x64 and all my games in all their 2560x1600 glory.
If I had to pick only ONE computer, I'd pick the Air. It can do almost everything I need except hard core gaming, and that is fine by me.