I have the Stanley "contractor grade" block plane. Long story short, it gets the job done, but it's the tool I'm most eager to replace.
The long version: Flattening the sole on this thing took HOURS, and I started with 60 grit sandpaper (that's not a typo - 60 grit). Getting the back of the blade flat was also a feat rarely achieved by mortal men. I love the block plane - the idea of it, anyway. I reach for it all the time, but the performance of the Stanley is very average. This is definitely a case of you get what you pay for. My advice is, if you see yourself using this tool a lot, then skip the big box store El Cheapo, and get something nice. I want to replace mine with a Lie-Nielsen.