tbh, I am not sure how else they could do this! If everyone hits the site at the same time, the system would not cope. At least this way, you don't have the site crashing.
it is very frustrating waiting 15-20 minutes only be be told there is no tickets, but I suppose all that has happened is someone ahead of you in the queue got there first.
Not really any different to joining the queue at an actual sporting venues (i.e. Wimbledon). There is one long queue, and 10 ticket booths. If you're further back in the queue, you may end up getting to the front to be told everything has been sold!