I live 15 minutes from Downtown (without traffic of course) and the only reason I would ever live there is if I actually worked in downtown.
I know two couples (no kids) who just bought down there, but they work about 20 minutes away. I think the novelty of living there that attracted them. The prices are not much better than an average home right now.
I say let them build all they want. It can only serve to speed up the correction. It will be a while before Downtown is the “5th AVE of LA,” and I agree there are more “big backers”, but I think most of them would rather find a place for their family, which downtown is not.
Everyone says there is no room to build in LA as support for maintaining high prices, but they always find a way. Lofts are an example of that. I tend to think they will be sitting on excess inventory in a few years, and maybe then I’d consider one.