We went on tuesday at the 10am slot. I agree, book the earliest slot available, because by the time we came out, the queue was enormous! They do stagger the entry, but even so, it looked terribly busy. I'd also avoid the weekend if you could!
Note, that I found it to be a complete money making scheme to get every penny from you as possible! Cloakroom charges were (I think, £1 for a coat or umbrella and £3 per backpack!). I just kept mine and walked around with it.
As soon as you walk in, they pull you to one side and snap a photo! I didn't even both getting the price at the end for it, but assume it would have been pricey.
I had pre-ordered the £5 audioguide, but wouldn't bother. In each room, less than 1/3 of displays actually had a link to listen to more info, and the majority of the info was already written on the display!
We didn't do the VR experience (more cost) so cannot comment if it was worth it.
The 'shop' was full of the most tacky items. £42 hat, similar to the type Hawass wears, a book by him for £40, plastic rubber ducks for the bath that were wrapped like a mummy and all manner of cheap tat at ridiculous prices.
The actual displays were clean and clearly labelled, but there were only 5 rooms in total, and it was very expensive. We took out time, read the displays, and were done within an hour! If it was busier, it would have taken much longer though.