To be honest after returning from Port Aventura they do exactly the same throughout the day, granted whilst the park is open longer rides open late and close early, some only open at weekends this time of year!
At 10am we had the option of Furious Baco, right by the entrance with an hour queue at 5 past, Rapids, Train and a few children's rides. Shambhala and Dragon Khan don't open until 11, with rides like Stampede, El Diablo, Log Flume and the drop tower not opening until 12.
Whilst I don't want to defend Alton Towers for this, I think it could be a lot worse as a fair amount of rides will be open with the park.