The three different platforms I'm researching at the moment are:
Sun recently introduced a dual SAS disk kit for the T1000, which actually makes it usable as an app server, price wise it is slightly pricey (the 2x72Gb SAS kit is about 650GBP (1000USD)), and it's single PSU. The T2000 would have been a better choice but the cost is simly to high. The biggest benefit it gives is it's top speed with huge amounts of threads and the fact it runs Solaris. We're quite likely to run several Jboss instances on these boxes so running these in Solaris containers is quite a good benefit.
I presume most people have seen the amazing Intel benchmarks of the 5100-series CPU's. It just flies. Trust me here, I know a lot of you probably hate dell kit, but the Dell "9-series" is pretty darn good. Pretty decent remote management with the new DRAC/5 card (it is in fact better than the LOM in the galaxy line (X4100 etc)).
Quick summary (for midspec machines with 8Gb RAM, procs as listed and max number of 72Gb SAS disks and an extra dual port NIC in the 1950):
|Sun X4100||Sun T1000||Dell 1950|
|Processor||Dual AMD 280 4-cores||SPARC T1 8-cores||Dual Intel Xeon 5130 4-cores|
|Disks||4x SAS||2x SAS||4x SAS or 2x SATA|
|NIC||4x GIG||4x GIG||2x GIG|
|PCI||2 PCIe||1 PCI||2 PCIe or PCI-x|
I'll post my decision when I make it. I have to say I'm leaning towards Dell at the moment.