We took our first trip to Legoland in April with two boys, aged 6 and 9.
For those who weren't aware of the history,
Lego (or the company that runs theme park operations for Lego) purchased the defunct Cypress Gardens park out of bankruptcy and spruced it up and re-themed it to Legoland.
Overall, we had a pretty good time at the park. I'm not sure what the "sweet spot" is for ages, perhaps right around 7-8. As kids get older the rides will definitely lose interest for them as they are designed with younger children in mind.
I was quite bored until we hit Miniland. As an adult the experience of exploring Miniland makes the admission worthwhile. I started to obsessively photograph all of the areas before quickly realizing it was so vast and there are so many details it was near impossible. The Star Wars scenes were particularly great.
The day we were there the park was quite empty (being an off-peak time in general), but despite this they still tried to sell "Preferred Parking". In reality they could have just fit every car in the lot in the preferred section based on how empty it was. We decided to trek across an empty lot instead of paying $20.
One thing that struck me about Legoland was how HOT it was. I find this interesting as I never notice the heat in any Disney park. I don't know if Disney makes better use of shade trees or there is something different about their pavement that doesn't reflect the heat as much, but Legoland was oppressively hot.
If you are planning on visiting, definitely be on the look out for the "free child admission" coupons that are usually on the back of the small lego polybag kits. (The ones that sell for $4 or so near the registers of Target/Walmart). Like any other theme park, it is not a cheap visit. Getting free child admission definitely brings the price into line with the value.
We will likely visit again, but it won't be a yearly thing for us like Disney and Sea World are. There is a new land being built based on the new Chima theme. I'm not sure when that is slated to be finished, but we will probably wait till that area is open before visiting again.