I don't suggest to use the walker either, I have a 21 month old and he started crawling at 71/2 months and crawled for 7 months which actually is good for him as he has very good co ordination. Also because he's a late walker, he is a very good talker as he now speaks in full sentence and knows what he wants and understands alot of things we say. We did let him use an exersaucer to practice his leg's strength which is not bad either coz they can entertain themselves and learn to balance. An exersaucer has a curved bottom so they will wobble but learn to balance.
After read "melodyuen"'s message, i'm so scare.mouth: I just buy one today as my BB always wants to stand up. But the one i bought cannot let her to walk around, just help her to stand.