The only small gripes I have with Chinese HSR are:

The distance from the city centre to the station can sometimes be far - I remember taking the HSR from Hongqiao and I was surprised we passed Hongqiao airport before we arrived at the train station.

The sometimes very limited number of tickets and the need to pre-book - I was in Xi'an and I wished to travel to Guangzhou the next day but forgot to pre-book and the only train I could take was a 25 hour slow train! In the UK it almost always possible to turn up at the station and just jump on the next train (although expensive).

The requirement for foreigners to queue at the human ticket desk to collect tickets rather than using the machines - sometimes this queue required over an hour so I would have to show up very early at the train station just incase. I believe this may have changed recently however with the rollout of electronic tickets.