Why else would any one use it? Email id on your own domain name and not looking suspicious as spam.
2. Sync on all platforms
Owning an OS X device & Android, this is an blessing.
Staying away from noise. Most things happen in Facebook but the important ones still on Gmail.
Pretty much turn of Google service to the minimum. All I have mail, docs, contacts, finance, G+. Compare this to normal Google account where every new service & product will be enabled by default.
Upto 10-users Google Apps is free. Can't find an free alternative for hosting email on my own domain. Fastmail, Hover and all are bloody costly.