Chipmunks, I persevered for a number of weeks with my DS at the first preschool but he just didn't settle, crying, and having nightmares etc and it was definitely getting worse instead of better (he was 2 years 9 months by the way). If your LO seems fine with it, then maybe it's just YOU that's worrying?
I turned up early a few times at the first nursery, and peeped through the door, and it seemed to be a lot of (the younger) children including DS1 just wandering around looking a bit lost, not sure what they should be doing etc, and the staff just shuffling around too! My gut feeling was that it just wasn't right for HIM.
By the way, I actually switched him to afternoon sessions as well at the new nursery (as DS2, baby at the time, was not a good sleeper and we were struggling to get out of the house in the mornings for the first preschool!). At his new nursery, the afternoon sessions are not QUITE as busy and structured as the morning sessions, as they cater for some children who stay all day and so keep the afternoon sessions a bit more informal and laid back. The staff were great though, as they always made sure that afternoon session-only kids got their turn at doing the craft activity or whatever that the morning children had already done before lunch. The following year when he was nearly 4, I switched him to mornings which were a lot busier - more kids etc etc, and more structured, and that was fantastic preparation for school. I think he revelled in the structured envrionment of the busy mornings, but he has always been a bit like that anyway - at weekends he'll wake up and say to us "So, what are the plans for today?" I think the average boy doesn't actually like a structured nursery environment - the stereotypical preschool-aged boy can't concentrate for that long and just likes to run round with his mates, or crash the cars into each other! My son wasn't like that, and concentrates really well and hates any type of disruptive behaviour in the class (I'm sure that will change when he's a teenager LOL).
Not that all that has got ANYTHING to do with your post really - I'm just waffling as per usual!
My point was that if your LO is fine with the free play environment, then I wouldn't worry about it yourself. There's plenty of time to learn a more "structured" way of doing things once he starts Reception. All that's required of them when they start school is that they are able to listen to the teacher and carry out instructions, and sit quietly for a short period. They will learn that during circle time and story time at both a "free play" type of nursery environment, or a more structured one.
Maybe the only advantage to the type of nursery that my DS eventually settled at was that it suited his anxious personality at the time. I have sent my DS2 there just because I like and know the nursery and staff, but he is very socially confident and it may be that he would have been fine in the free play type of pre-school that his elder brother first started at.