I just installed CM7 last night, first time with CM, and I already miss the HTC Mail app.
Before I used the Gmail app (with Gmail Unread Count in the market) and had all my other accounts in HTC Mail (Exchange, Yahoo's, AOL's, etc). The HTC Mail app has folder and move support on all account types. The regular Android mail app does not, and nothing on the market is quite as good. Plus, the HTC app works with Yahoo, AOL, etc without having to be a "Plus" user of all those services. The latest versions of the Android apps do three things I don't care for:
1. No longer allows non-Plus accounts to login.
2. Supports & enforces Exchange device administration plugins.
3. No move support in Exchange or any other account types.
The woman's Epic finally has that ability in the Samsung variant of the app, but that too can't be installed on a ROM without also installing TouchWiz.
Looks like I'll have to go back to a ROM with Sense installed. Really wish HTC would put their mail app on the market like they did with the original version (called Work Mail).
If HTC made their mail app support multiple Exchange accounts, I would likely use it for Gmail as well because (as stated above) the HTC mail app allows you to set when you don't want it to receive.
Granted, in CM7 it supports Quiet Time to prevent audible alerts when you don't want them but it isn't the same as telling it to just stop.
And the only real bug in HTC Mail that I would like to see fixed is the Exchange daily check bug. Let's say you like to have your work email not check at all on your days off. Well you can tell it to do Manual, but it will still check once a day. The problem is that once a day check that you can never stop from happening is based on the exact time the account was created in the app. I had added my work account after a reformat one night at 3 in the morning and for a long time couldn't figure out why my phone was pulling my work email at 3am every night no matter what I did to stop it. Finally deleted and remade the account at 5pm and it started happening at 5pm everyday it was set for manual. Not as annoying, but still stupid that it isn't fixed.