It is potentially viable today. Chromebooks and Chromeboxes are already using it. Mobile devices already use it. If you are okay with not running Windows or Mac desktops, you can run most Linux or BSD desktop configurations on it now. So end user computing is already pretty much there.
If you do any non-Windows server work, ARM is already very viable for SMB servers. Web and application servers, databases, LDAP, etc. all will work very well there.
