After hearing the buzz about Gmail offering IMAP access, but also hearing that this new feature wasn't rolled out to everybody yet, I decided to check if my account had it. Sadly, it didn't look like it and I thought, maybe it's because they're enabling it for the earliest Gmail users first.
Then I checked out the Gmail blog which explains that the feature is actually available for all Gmail users. Then why wasn't it listed under my Settings? Because Google has only rolled it out for those using Gmail with the US language and will be working on the other languages in the next few weeks. I, being the typical Anglophile, had set my account to display UK English and thus had prevented myself from receiving IMAP access immediately.
So I switched to US English and voila! IMAP was enabled.
I'm now watching Thunderbird load up my mails. All my Gmail labels are appearing as folders. Wow, I haven't had IMAP mail since University days. This should be pretty useful.