My daughter absolutely loved it!
The Rainforest Cafe is a really fun place to bring your kids - I visited with my little girl last week, she loved meeting cha cha and seeing the jungle. The food was absolutely fine, just don't expect high-end dining. The price is a little bit on the high-ish side, but given the location (smack bang on Piccadilly) and the effort they must have been through to make the restaurant look so amazing, you can't really complain too much. My daughter loved it and that's the main thing!