We enjoy an occasional visit to Rainforest Cafe. We've been to the ones in Overland Park, KS and The Mall of America. Personally, I would never go to the ones at DL or WDW because, well, I can go to one here at home. If you don't have one where you live, it may be more entertaining.
I have always found them to have slow service. That's intentional, I believe...they encourage the kids to wander around the restaurant to see everything. I've also had a couple of major glitches there. Once, they "lost" our name, and we ended up waiting almost 2 hours to be seated. Another time, just after receiving our food their power went out. The place is like a cave...it was pitch black except for emergency lights over the exits. The rest of the mall still had power. We couldn't even see to eat, so after about 10 minutes I asked for to-go boxes. We were offered no apology and no compensation.
Since that little debacle I've become much more selective about going there. We've only been once in the past two years, where we used to go 3 or 4 times a year.
The prices are high for what you get. I also found it a very difficult place to eat when I was pregnant...lots of their recipes have soft cheeses or bleu cheese in them. That said, my favorite there is the crab cakes. My boys either get the nuggets (dinosaur shaped ones...same thing you can buy at the grocery store) or pizza (kind of like a big cracker with sauce and slabs of cheese on it). The portions are large...but large portions of mediocre food, well...
As you can tell, the only reason we go there is for the entertainment value. If your kids have never been, I say go ahead and eat there. If you've been before or if you have one close to home, I say skip it.