For me, it crashes...it locks up and won't do anything. I end up having to use the task manager to shut down maya. Sometimes it locks up like that, sometimes it says memory error, sometimes it says fatal error. But it only happens when I start getting up to 1.5mil polys.
At about 750k polys everything starts slowing down but still workable. I just put things on layers and only keep a few things on my screen until render time. I need to learn how to composite, then I could render in passes and composite them. But right now I don't know how to composite.
Don't be satisfied with what you can do but rather strive to do the things you can't do!