I run winblows on my lappy, ubuntu on my PCs (work and home).
I run remedy in WINE. The only thing I have problem with is the Remedy email system, which you guys don't use.
We don't use exchange at Tech (at least, not as a whole... some departments do, but not OIT). I use IMAP in Thunderbird to work with SPECTRUM email, which is home grown as far as I can tell. Have you looked around online for this at all?
As for calendar support, we're currently changing systems. Right now I merge my work calendar into google calendar, and I hope that process becomes easier with our new system. I like google calendar a lot because I already have it integrating with my phone (it sets itself to vibrate automagically when I'm in class or a meeting).
I suggest dual booting as a test for your specific programs. Look for open source/linux versions where you can, and try out WINE where you can't. If you can get all your required programs working like I have, it turns into a superior system in my opinion. Of course, my #1 program used is SSH for remote access to switches and routers, and cu for local access to switches and routers. I let remedy tell me when I have a ticket, and we have a fully functional web interface that I use sometimes. Usually I only log into remedy to CLOSE a ticket, but that's how most of my tickets are (the request is made, I fulfill request, I close ticket).
All of our SAN backup guys use Linux on their machines, but I don't know what special purposes you have for the programs you listed. Java-based programs probably have a linux version.
I think you shouldn't go to Linux if you need IE... that's simply not going to happen.
This will tell you how to do just about anything:
http://ubuntuguide.org/wiki/Ubuntu:Feisty