From the little of it I tested it's okay. I managed about 30 FPS at best in open world Morroblivion content despite getting 60 FPS in open world Oblivion content. That's about the same frame rate I get from actually playing Morrowind with the MGSO 3.0 overhaul installed, and MGSO actually looks better than Morroblivion for most everything except a few odds and ends like humanoid character models. The landscape is gorgeous and the night skies put (vanilla) Oblivion, and even (again, vanilla) Skyrim, to shame.
If you can't get Morrowind to play on your PC for some reason I would imagine it's good enough to get the job done, but if you can play Morrowind as well (and given that you rather need Morrowind's data files for Morroblivion the assumption that you have both is valid) your choice is really about which set of bugs and mechanics you want. Do you want a few extra skills and combat mechanics where you can swing your sword at a mob in front of you that happens to be standing still and miss, repeatedly, and different ways to (ab)use the mechanics to your benefit/enjoyment or do you want more or less the standard Oblivion experience in Vvardenfell?
Personally I'll take Morrowind with MGSO over Morroblivion simply because it's less to go wrong with Oblivion when I want to play actual Oblivion content.
Stop complaining. I could have done this more painfully. - Dryad from Sacred 2.