Have you had your baby in a walker.?

I have been advised not to use the walker (I have 2, one that moves and one that is stationary) and my 6 and a half month old son loves it, he is at the stage that he does not want to lay down anymore. Has anyone ever actually used a walker for their baby and was there any problems later down the track? EG: Operations on Achilles heel, walking on their toes etc. Or was a walker used and there was no problems ?