I have bought three pairs of cheap platform pedals and one decent pair, and they all came with bearings that were too tight. These all had traditional cup/cone bearings with loose (i.e. not caged) balls. It was possible on all of these to pry the end cap off, loosen the lock nut, slightly back off the cone that is accesible from that end, and then retighten the lock nut. That's the theory anyway. In practice, it is a pain to lock these down right at the point where there is no play and no friction. The reason is that it's hard to prevent the cone from turning along with the lock nut when you are tightening it. Needless to say, it's really nice when pedals come out of the box with the bearings adjusted correctly.

Edit: To try to answer your question, I haven't noticed that having tight pedal bearings is really that noticeable when I'm pedaling. I just don't like the thought that the things is wearing out faster than necessary.