I guess it depends on what your friends use. I have never sent an MMS. Not once. If I want to send someone something, it's sent as an e-mail attachment, since pretty much everyone I know gets their email pushed to their phone.

Also, the App store is not a necessity when you have an open platform. No doubt, it's VERY convenient, but when you can download anything to your phone it's less of a concern where it comes from.