Matts (email not shown publicly) I work for MessageLabs [messagelabs.com] in Toronto, ON, Canada. I write spam filters, MTA software, high performance network software, string matching algorithms, and other cool stuff mostly in Perl and C.
It's the little things that irritated me (compared to my mac)
Shutdown/startup from sleep isn't instantaneous. This is a brand new IBM running XP. How can they not have gotten this right yet?
Double clicking an IP address doesn't select the whole address. This works everywhere on my mac - in the browser, in the terminal, in the mail client, etc, and given my job involves a lot of work with IP addresses this proved really frustrating.
Alt-tab doesn't switch between apps - it switches between windows. Really annoying.
Alt-tab's little window display isn't selectable with the mouse - how easy would it have been to implement that - it's incredibly useful when you have a lot of windows open.
The cmd/cygwin window. Ugh. Just ugh. How can people use the command line on windows with that thing? Just horrendous (is there a free replacement anywhere?). Putty's window is much better, so I ended up installing sshd and ssh'ing to localhost. That's f*cked up.
Personal preference, but I don't like the mail clients (prefer Mail.app).
I missed Safari's RSS viewer. Why doesn't firefox's list how many new items there are?
It's amazing how much real-estate is wasted by each app having its own menu bar.
Back to the mac now. Feeling much more productive already:)