We've been here for a few days out in recent years -- but we've stopped going now as o be honest we weren't very impressed. The place is expensive, and whilst it is possible to find vouchers etc to reduce the cost it still feels over-priced for what it is. But the biggest complaint is the tacky feel to the place -- it looks cheap and plastic, and not the sort of place where you'd be comfortable spending a whole day (which you'd have to to make the entrance fee worthwhile). There's also a shortage of places to eat lunch, which is awkward because it can get very busy (particularly in the summer holidays).
On the plus-side, the animals seem to be well-cared for, and there are quite a few demonstrations etc -- but all in all, I'm afraid we're unlikely to visit again.