Visited the centre on a Monday in July, it was still quite busy so I’d imagine on a weekend it would be really crowded. It really is a massive place so wear comfy shoes as you’ll be doing a lot of walking!
Bad points: some of the roof is glass & it felt really hot in there with the sun beating down. We did visit on a very hot day & it’s a big place to keep cool with A/C, so in warm weather dress appropriately. It felt uncomfortably hot. Also, I felt that there wasn’t anywhere near enough seating. I know it’s probably designed like that: if you’re sitting down you’re not shopping & spending money, but a few seats for you to take a quick breather would be very welcome.
Good points: for a place so big & busy it was very very clean. I saw barely any litter & there are plenty of bins around. Hats off to the staff who obviously work hard to keep the place looking clean & tidy. Also, I didn’t have to queue once for the toilets. There are plenty of them, they’re well signposted, & again, very clean. Finally, I thought the parking charge was very reasonable for London - £8.50 for up to 10 hours is great value in my opinion.