I've used all, and 3/4 the most and 5 more recently.
Everybody seems to have very high opinions of takion. It's created by the same guys who created andover/anvil (before it was bought by sungard and then by LS before they shut it down). I think lightspeed is better than many of these platforms, even though it's not on your list (maybe because you already use LS and want to move? dunno)
here's how i'd rank them based on my own .02
1. takion
2. ls
3. das
4. sterling
5. laser
6. fusion
cheers
