Would you recommend caster wheels?

[lawnstar]

I recently bought a Poulan 21" push mower (rear wheel drive). It works great, and I'm pleased with it. But the thing is, I was used to using my generous neighbor's mower, which had swivel/caster front wheels. They made his mower far more maneuverable. I kind of want to try replace my front wheels with swivel wheels. Are there reasons not to do this?

Thanks in advance for any feedback!