The booking process with "Travel China Guide" was fast and flawless and the tickets were provided on time before the visit, all communication with the company was exceptionally friendly and helpful - their webpage contains a lot of information, is well structured and easy to understand and use.
On the day of the visit the tickets could be used as expected without any issues. The Summer Palace itself including various points of interest, gardens, a big lake with boats to transverse etc. is extraordinarily beautiful! We have spent hours on site to see and do everything and it was very enjoyable, the reachability per subway as explained by "Travel China Guide" is fast and easy.
If you want to visit this splendid place I recommend getting the tickets via this company, then you don't have anything to worry there (or queue) but simply pass the gate and have a great day.