I've had one for about a month and I give it a good spraying after I use it, and I also have one of those brushes that hold detergent and that's all it takes to keep looking nice. The corners haven't presented any problems at all.

I have no issues with my square corners either. I spray it and wipe it with the square edge of a sponge or even just with my dishrag. It's really not anything to worry about. I LOVE my sink!!

Our friends bought the sink with square corners and they say they hate it. We ended up buying one with slightly rounder corners because of that and it is much easier quicker to clean than theirs is. I think they're going to end up replacing it with the same sink we bought. We got a Kraus 10" deep sink from overstock.com and I've been very impressed with it so far.

No problems with ours (almost 7 1/2 years).

I also have the Kraus. I think it is 7/8" radius. I got that one after I heard about people cleaning their square corners with Q-tips.
It is REALLY deep, but luckily I am short enough to reach.
I like it. But I am not an obsessive sink cleaner.