Good Question! To my knowledge there about 10 known companies working on ARM based Micro servers, I guess most likely performance per watt will be very close among all, it will be a tough market unless there is a key feature differentiation!
I'm happy to see Freescale adopting the ARM ISA. One of the best outcomes would be to see Freescale merging some of their more valuable "legacy" IP with the newer architectures. IMHO one of their best features was the Time Processor Unit (TPU) which was available on the ColdFire processors and was also brought into the PowerPC uCs. If you've ever tried to write and support a complex application using the generic ARM timer you'd understand how much code development it really takes. If Freescale decides to start designing ARM uCs (and especially in it intends to de-emphasize PowerPC for these applications) it needs to seriously consider integrating TPUs into such an architecture, both for new designs and to support legacy code bases to give them a reasonable "upgrade" path.
Every ARM 50 licensee would have their eyes on this market. Other than AMD all the existing licensees have been embedded players so they are most likely intent on retaining or expanding their market share there. The server market is a huge lucrative space that they can target if that does take off so it appears to be a low risk approach.
The question on differentiation remains. In the embedded market that is in the SoC with the special accelerators etc. In the server space it is primarily about the CPU so while there will be slightly different variations to memory interfaces etc. they will most likely look alike. Which means the only differentiation will be on price - which makes the business folks at Dell/HP salivate at higher margins....
This doesn't really come as a surprise. We can't know whether Freescale will succeed in the ARM server market, but they can't realistically stay *out* of it. There are too many markets Freescale would like to be in where ARM is the architecture of choice, and if they want a piece of that market they offer ARM cores.