I tried to use MailDroid and k-9 mail a while ago,back in October, but neither of them supported Exchange 2003 at the time which is what my company uses. I went out today to check them out and they both now support Exchange 2003, but I have been using Touchdown for exchange and it is awesome, but I don't know if I want to pay 19.99 for just exchange support. The things I like about touchdown is that it is push for exchange and support activesync. It also has an integrated calendar and nice widgets to boot (e-mail, calendar, tasks, etc.).
Does anyone know if Maildroid has an integrated calendar as well or is it just e-mail/folder support? I see it has a calendar folder which lists all events, but I don't see a calendar.