people may not agree with me, but from past few months I have seen improvements, i am able to book tickets at 8am smoothly when I try to book for 2 months advance, earlier i used to get "service unavailable" very frequently. now by 8.03 or 8.04 max i m able to book tickets. the reason may be moving tatkal opening time at 10 am or something else. haven't tried booking tatkal though, i know there are issues when booking tatkal.