The first company I worked for was pretty much a Windows-only shop. They used Exchange for email, VSS for version control, and Visual Studio as an IDE. This was the first time I had ever used Windows, and I disliked it (although not as badly as I thought I would) — but I didn't really have a choice. Since 2004, though, I've been fortunate enough to be able to use Linux on my primary dev box at work. My current company (and all the ones I've ever worked for) still uses Exchange, so I've struggled with how to deal with this over the years.
Now Dasher! Now Dancer!
When I first started using Windows, I didn't know the difference between Outlook and Outlook Express (apparently the former is an Exchange client and the other is a generic SMTP/POP client), and so I used Outlook Express (because I wanted my mail faster, of course). After a few months I finally figured out why I couldn't "accept" meeting requests: I needed to use Outlook for that. So I switched to Outlook proper; and even after I moved my primary dev box to Linux, I still kept a Windows machine on the local Windows domain to keep using Outlook (and also to test IE, of course).
Now Prancer and Vixen!
But switching back and forth between my Windows and Linux boxes got old pretty quick. First I tried Eudora as a SMTP/POP client (which I had used on the old Mac OS before OS X). That was okay, but POP is pretty primitive and usually doesn't work well (it's hard to keep the local read/deleted states in sync with the server, so you usually just end up downloading everything locally and deleting it on the server — which means you better have a good local backup story).
On Comet! On Cupid!
Then I tried Evolution as an IMAP client, which works (at least with Exchange) much better than POP. You can keep mail in sync on the server, and even use Exchange's server-side folder structure. The two big things missing still, though, are contacts and meetings. Evolution is supposed to be able to integrate more tightly with Exchange (possibly including these two features) via Exchange's web interface, but I've never been able to get that to work. So I just used Exchange's web interface whenever I wanted to lookup a person in Exchange, or to schedule/respond-to a meeting.
Eventually I got restless, and decided to try Thunderbird. I can't say that it's really any better or worse than Evolution, just somewhat different. It's what I use now, but it still doesn't have contacts and meetings (although for a while I got it little bit of contact integration by syncing it with the corporate LDAP server). But then one day I found Lightning (and you're welcome for taking so long to get to the point of this post).
And Blitzen! (aka Finally, the Point of this Post)
Lightning, an extension for Thunderbird, allows just enough integration with Exchange's meeting functionality to be really really useful to me. Lightning is mainly a calendaring extension, but it's also able to parse Exchange's meeting-request emails — it displays a button right in the email to add the meeting-request to your Lightning calendar. So now I finally have a way to organize my meeting schedule (other than to highlight the meeting-request emails in my inbox — plus in the past Exchange unhelpfully moved these emails to a separate Calendar folder if I used the Exchange web interface to accept the meeting).
Here are some pics of the Lightning "Today Pane" (displayed on the right-side of my normal email listings), and the full Lightning "Calendar" interface (which is pretty much exactly what you'd expect and need from a calendering UI). My apologies for the super-gay Thunderbird persona (I can't seem to login to the Personas website in Thunderbird, so for now I'm stuck with picking one of the "popular" personas).
Lightning "Today Pane"
On 64-Bit Linux
The one gotcha with this (and kind of my motivation for writing this post) is that the version of Lightning from addons.mozilla.org doesn't work on 64-bit Linux. Fortunately, Ubuntu has this documented and taken care of on their ThunderbirdLightning Community Documentation page. To make it work, I just had to download the 64-bit lightning.xpi, and install it manually (via the Install... button in the Extensions tab of the Add-ons dialog, which you can get at via the Tools > Add-ons menu item). Now dash away, dash away, dash away all!