The pain of maintaining this long term (look at those CSS identifiers with jibberish names, you know those aren't set in stone) is going to be worse than the pain of adapting to crappy Gmail.

You know what else sucks about Gmail, other than just the design?

* There's no option to consolidate multiple emails into a single thread (so you're at the whim of the sender to maintain the same thread)

* There's no "Send after X duration" or "Send at X time", so you can't write something at 3am and schedule it to be sent during work hours. [Edit: I stand corrected, there is a Scheduled Send option now]

* There's no way to add private notes to email threads. So if I'm told something over the phone which is relevant to the email conversation (but private), I have to dump it into some other notes app where I'll lose it. [Edit: No, confidential mode is not what I'm looking for]

I've said the same thing about FastMail before, these email guys SUCK at innovation.

The only thing good about Gmail is the spam detection and the superior deliverability of using a Gmail address.