On PowerPage Podcast Episode 71 I discussed the sluggish behavior of MacBook Air and slowdowns in Microsoft Excel:mac 2008.
A colleague (Joe Gudac) doesn't think that the problem is related to the MacBook Air. He's run into the same problem on an iMac (2.4GHz with 4GB) and MacBook Pro (2.2GHz with 4GB) but not on an older iMac (2.16GHz with 3GB).
For me the problem is with Excel files (usually created on Windows) that I open from a Windows Small Business Server 2003. After a couple of minutes there's a noticeable lag while typing and tabbing between cells. If I type a few characters, tab, type, tab, type, tab it will sometimes still be typing in the first cell when I'm in the fourth. Eventually it catches up, but I have to stop typing for a while. New files opened locally perform normally.
I also have incredible problems printing many Excel 2008 files to a Lexmark E240 printer (driver version 10.5.0.0), many times the files (created on Windows, opened from the SBS 2003 server) crash Excel on print. I thought that the Office 2008 12.0.1 update fixed the problem, but it still crashes Excel on print.
I took a look at Activity Monitor on several of my Macs and I noticed a process running named "kernel_task."