We went for the first time in 2009 just so we could say "been there, done that". Now we say "been there, will never do that again".
Its large but not humongous. It didn't appear "dirty" to me but the crowds were worse than any Disney park Ive ever seen on any summer month - and thats no lie. It was so crowded you just stood, and stood, and stood...hoping for someone to move so you could simply pass by. It took 45 mins just to get to the counter and order our food. This was on a weekday, in the month of October.
They have lots of games, and of course they cost money. And your kid will get a 1 inch plastic lizard (or something of the sort) if they get enough points/tickets from winning games.
I would never, ever recommend this McDonalds to anyone simply because of the craziness inside due to the crowds.