Parallels works great for me.
I work for IBM, and Mac Airbooks are the #1 choice for those of us who get to pick our hardware, although the Samsung 9 is gaining popularity too. I run the client image under parallels and while there are some focus problems, it is worth putting up with it.
Why? I can carry one very light laptop for personal and business use. Turn the VM off, and all the IBM "security" ware is disabled.
The battery life is a little worse than other IBMers get running the native WIN7 image or MacOS + IBM client software.Running the MacOS version of Lotus Notes sucks power just as fast as any other version, emulated just adds a little more. Running Win7 sucks even more.
Most Win7 users immediate switch to MacOS+Parallels once they see how well it works. For most the only reason they need Win7 is for spreadsheet support. Mac "native" version of Excel has some serious problems with Macro support and large numbers of rows.
Not sure about Linux, have yet to meet anyone running Linux on the MacAir yet, and IBM supports all the major distros as a desktop client.