Recently, I discussed with several clients who were planning to or made the switch from their V890 servers to T5000 Sun Server.
If you're considering this change too, please notice that these TX000 servers are excellent for handling heavy loads,
but as their architectures are based on CMT CPU, simple operations that cannot be parallelized are simply (much) longer.
And unfortunately, when an app server starts, it's a succession of tasks, that were not designed to be simultaneous.
I can tell that a large application, deploying in 5 minutes on a V890 did exceed 20 minutes on a T5000 !
But once the application is deployed, a better behavior has been observed under a strong load, for the T5000.
But, I guess you have to know it before you take that kind of decision ...