I'm not advocating that people move now. The value of Gmail definitely outweighs current costs for many people so it makes sense to keep using it. But to buy a domain and forward email to a Gmail address does not require a VPS or maintaining it.
Other services may be harder to migrate, but they usually don't have the same cost of notification. If I change where my calendar is hosted, I don't need to inform all my contacts.
Again, a Google Apps account for a single user now costs $5/month ($50 if you pay annually). I made an account (with multiple users so I could have different emails for certain services and needs) when it was still free. If I were to sign up now, I'd need at least 4 users, so it'd cost me $20/month.
There are better and cheaper alternatives, but I just wanted to point out that you can't get free Google Apps accounts anymore.
Other services may be harder to migrate, but they usually don't have the same cost of notification. If I change where my calendar is hosted, I don't need to inform all my contacts.