Saw the Jeff Koons exhibition here this Summer. The gallery is free to enter, and invites donations, sells guides etc. We walked straight in, but as we were leaving there was a queue, and a few people being let in at a time. I was impressed by how smoothly that was being managed (okay, not a tricky operation, but some places do it without much charm!). The staff were keeping people informed as the line moved (fairly quickly), advising them about not touching exhibits once inside, and carrying backbacks rather than wearing them etc, and offering the couple-of-quid guides to anyone who wanted one whilst waiting.
A guided talk started part way through our visit, and we decided not to join it, but when they caught up with us we wished we had. The guide was really lovely, very well informed and interesting, and not at all patronising in response to questions (I've heard some guides some places can be intimidating, though I've never experienced that). He had had contact with Jeff Koons and was able to talk with authority about the artist's career and current show. I learnt a lot and it enhanced the exhibition for me. The talks are free, I believe.
It was a very smooth gallery experience, and a lovely space in which to view the work. It's quite small - you could spend a relaxed hour on an exhibition. We could have enjoyed looking for longer.
We also went for the Pavilion which is designed for the space outside the gallery by a different architect each Summer, and worth a look (I was there mid-August) That was very enjoyable; we sat underneath and had lunch from the little cafe bar that operates just outside the gallery (and is part of it). Very pricey for take-away (even for London, I thought - I'm fairly sure it was £3.60 for a bottle of 'This water'), but given the setting, and the fact that the sandwiches really were very good indeed, and of quality ingredients, it didn't seem unreasonable on the day. (Only one complaint, which I emailed them afterwards; they didn't accept the glass bottles back for recycling. My personal opinion was that they should!).
The gallery and pavilion didn't feel crowded at all, even in the middle of August, though it was very well attended. It felt like an airy and tranquil place to spend a couple of hours, and a lovely setting, and next time I'm in London I will definitely check what's on there.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC