I think about 3pm Eastern time(GMT-5) to 11pm Eastern is pretty solid because you get a solid crossover from multiple time zones for example, 5pm Eastern Time is:
- 6 pm in Most parts of South America
- 9 PM in the UK
- 10pm in most parts of Europe
- Noon on the West Coast in the US
I'd be interested in other opinions, but I think that is probably the busiest time period of the day, with the most selection of games. Sometimes the really late(early morning games can be especially good because bad players are trying to get even or don't want to quit)
Jason