I've got several domains, I just forward them to my gmail account and set up the reply-to addresses if I want to be consistent - no need to get an Apps account for that.

We also run an email system at work, though it's a lot more work than other services - mostly due to spam / deliveriabilty - so even if you do pay $50/yr still seems a bargain. IMHO you need 100+ users to even think about justifying the time cost for running a mail server yourself.

Also, I get access to all the new Google stuff without having to wait for Google to make it 'business-ready'.