I'm on PS3, up until a month ago I was living in Hong Kong with a not very fast, but reasonable wired 8mb bb, I couldn't get on MK at all, NOT AT ALL, it just told me 'match disconnected' every time I tried to go into a match. I could join rooms and I could chat, I could also online game with SSFIV (bit laggy sometimes), Assassin's Creed, ModNation Racers and many other online games.
My brother who was back in the UK on a 20mb bb could also not get online at all, same issues, although he was trying to fight wirelessly, but SSFIV was perfect, no problems at all.
I am now at my parents in the UK (thankfully temporarily) here I am on a wired 30mb bb and finally I am able to fight matches, but usually I only get one or two ranked fights before it then stops finding opponents and seems to not be connecting correctly. It also still takes ages to connect to the MK servers initially and quite often it seems to drop from them and I have to give up online and return to offline fighting.
The point I'm trying to make is that it doesn't seem to matter entirely what your net situation is, they did a lot of things great with MK2011, but their net coding, or servers, or whatever, was not one of them. Some people seemed to have that perfect set of criteria that gave them no problems, but a huge amount of people didn't. The poor online experience is to many why MK lost players rapidly, they screwed up somewhere quite largely with that and I say this as someone who loves MK, in every other way MK is a more fun fighter than any of the others and I play it far more than I should.