I guess the speed of transaction is quick enough for all coins with 60s or faster block time. Besides, PoW/PoS coins have generally faster blocks than stated, because PoS difficulty being independent from PoW difficulty.
If i am not mistaken, then Fastcoin has had many problems because of its 12s block time?
I have not seen any faster coin than Fastcoin tho.
Remember that there is a trade off between block speed and block chain size. I think HBN has the perfect balance between the two.