It automatically saves the last like 10 or 20 replays, regardless of whether you saved it or not, I think.
Oh... well I'll check if I still have it. Why would you want to watch a replay of me losing, though? haha
So I can see what you did wrong and point it in your face.
As for motherships, they have area cloak, vortex and Mass recall. Mass recall works exactly like it did in SC1. Vortex is like stasis, except units walking into the stasis'd area after casting are also stasis'd. Basically it creates a hole in the map that anything sinks into, and after X amount of time the hole disappears, spewing everything out again.
The mothership is probably one of the most nerfed units in the game.
It used to have a bunch of sweet spells and abilities, but no surprise they were all overpowered beyond belief. The most recent spell removal was the teleport spell it had, where it could instantly zap to any place with a power field on the entire map. Fun matches of mothership rushes ensued, where the mothership would fly into opponent's bases, tear stuff up then whenever its shields were depleted (those things have like 800 shields or something) it would simply teleport back into the protoss base, then begin its long trek towards the enemy base again, regenning its shields as it went.
They're very difficult to use very well, though. I think one of the best uses of arbiters in SC1 was to fly into a locked-up terran base and mass recall a good squad of goons to tear down all of his stuff while his tanks were elsewhere. But the mothership is simply so slow that it can't sneakily surprise like that. Another use was the stasis, but vortex is not hostile-only, if you lead your own units over there they'll get sucked in too. A lot of mothership + carrier battles have been lost because the mothership created a vortex which nearly every single interceptor got sucked into, rendering the entire protoss force defenceless.