Gmail's web client also non-optionally auto-wraps text before sending, which is very annoying when you're trying to send a patch or part of a log file.
Is there anything I can do to tempt you to switch back to plain-text emails?
I think of it as 99%[1] text/html with format=flowed, and if gmail ever added format=flowed to text mode[2] I'd switch back in a heartbeat.
[1] The remaining 1% of the time I'm composing something long enough that it has more in common with publishing than 1-1 communication.
[2] I wouldn't hold my breath: http://productforums.google.com/d/topic/gmail/Z42NibAOzjc/di.... More likely I'll stop using gmail one of these years..