I have used Birmingham New Street many times. Many people say that it is an eyesore and that it is no good. On the contrary, i think that it is quite good and also efficient most of the time.
It is really quite confusing at times, and i wouldn't advise running around looking for the train that leaves in 1 minute under the influence of alcohol and an illegal drug :)
After you have used it a few times it is good. It is the busiest station in the country and there are plans to rebuild it all. It is quite convenient that the pallasades shopping centre is just under the station as it makes it easy for people to go shopping and get out into the city centre and next to bullring within a matter of minutes.
The really annoying thing is how they always change the platform with like 30 seconds to go so you always nearly miss your train.