Personally, I'm a bit of a hypocrite, because I use my gmail as my main account, despite being far more comfortable with a service I can pay for (in the past, that was MobileMe) and know I can get customer service on the phone. Honestly, once Apple can show they've got their act together for more than a few years I'll probably switch...
I do.
>They've already changed people's email addresses as least twice, which is beyond uncool (mac.com -> me.com -> icloud.com)
And they all still work.
>Unlike your username to their services, your email address is tied into all sorts of other third-party services (not to mention address books) and is incredibly painful to update.
Since the aliases still work, as mentioned above, this is not an issue at all. Personally I prefer to use the me.com domain as it's short. It still works and the services that I use with me still work, I continue to get email from them. The same is true with .mac addresses.