I don't recommend baby walkers at all - simply because they're unsafe. The ones with wheels can move enough to put the child in a precarious situation - falling down stairs, etc. Something like an Exersaucer, though, is fine. They can help strengthen leg muscles (turning, jumping, getting used to bearing weight) and have no risk of injury. I would be moderate with its use, though. Like with anything like that - don't use it as a babysitter, y'know?

What is the age of your baby? As Maggiesmom says an Exersaucer is great, as is a "bouncy chair" that can hang in a doorway (make sure there is a lot of clearance). They have made them very safe, and provides a lot of movement and motion

emerson is 5.5 months old - but he's a big guy - 20 lbs at the last doctor's visit three weeks ago

I don't believe much can change the natural course of what a baby is going to do. My baby won't spend more than a half an hour a day in her exersaucer (if that) so I don't think there coud be much developmental altering with so little time. Babies do what they want to do. I think any activity that your baby likes (and is safe) is good.