EDIT: I hate my KB. It has a tendancy of dyslexia, which isn't present on my laptop... oh well.
and what does this have to do with it?
A mothership costs a crap ton of resources early on, so unless if your oponent isn't agressive enough, or isn't scouting enough mid game, then well... one mothership won't make a single difference.
It's some 400min/300gas+fleetbeacon+stargate (which will remain unsused because of the sheer cost of the mothership - this all depends on timing, of course).
But an amply agressive Protoss player with enough units and production will never get to the point of having enough resources for a mothership, IMO.
HDstarcraft did cast one game about a month ago with a mothership play, but that was it. And it all came down to a mistake made in collosii placement & reinforcing units, not the mothership (though the final vortex sealed the deal).
My point is that P also has a unit which is generally never used and it's suppose to be the P's ultimate unit.
Seemed like the point of your post was to express your frustration with all the nerf's Terran has recieved and I was just calling out one of the examples you use. The fact is, we can all complain about any race. If you want to play me let me know.