Like the yellow "have a nice day" happy face intelligently exploited by its commercials, I always have a smile on my face when I step into "the mart." Though sometimes admittedly it is a cynical one.
There are times where the "express" line is slower than the regular lines. Once in awhile a checkout person checks-out and that also slows the process. Occasionally, one encounters children that seem to be running out of control and into things around nearby bemused parents. And these are things that definitely hurt my head.
However, if you know what you are looking for and particularly for everyday household products, Walmart can be a wonderful place. Recently, purchased a flotation device for an upcoming houseboating trip and the selection was such that it took me a good 10 minutes to make a decision.
It's huge, it's relatively price competitive and if you are not careful you can pick up more here than you intend to. Maybe that's the point :)