I can't point you at anything specific, but availability seems to be constrained, and the platform has been available for about a year, which is typically around the time that the platform will either be refreshed or retired. Seeing as how there doesn't really appear to be any future for the Turion, it isn't clear where HP might go with this. My impression is that HP is struggling to figure out how to cope with the evolution of their enterprise server business, and "experiments" like the MicroServer are likely to wind up scrapped.
This article is a sign of things to come.
We have an N36L here in shop; it's underwhelming. Don't get me wrong - it's not bad, but it's not great. The real problem is almost certainly FreeNAS and ZFS, because as you say the theoretical throughput this thing should offer is immense. We benchmarked it as being similar in performance to some of our older Opteron 240EE platforms, which theoretically should be able to swamp their gigE's, but under FreeNAS, they don't (and under FreeBSD with UFS, they *do*). I don't wish the N40L any ill will, but quite frankly I'm going to guess that you won't be able to buy them in six months, and I'd be shocked if you can get them in a year.
The way things have evolved here, it's not really practical to deploy a FreeNAS box for some of our applications. In a VMware environment, availability of the storage area network is very important, but it's very expensive in terms of watts to deploy an X86 based box, since it's difficult to get them sized such that they consume less than maybe 30-40 watts. Combined with ZFS's abysmal performance for iSCSI, we've done something drastic, at least for the short term - we've gotten some "desktop" grade NAS units. They idle around 5 watts (plus whatever the disks take) and are very responsive for iSCSI. We're using six of them as the foundation for our VM environment, and can lose at least two without a problem... redundant array of NAS devices, I guess, haha. But we still have a lot of drive bay capacity in the VM hosts, so running a FreeNAS VM means that we can use resource-rich boxes more efficiently. We just can't use the FreeNAS instances for the actual virtual machines, which kind of stinks.
In the end, I'm kind of disappointed that there isn't something equivalent to the ARM CPU's for X86-land that could be used for NAS. If an Atom, Via, low-end i3, or even Turion based system would idle down in the single digits, that'd be very compelling. The only thing I've seen like that is the Apple Mac mini, which is just too expensive (and locked into a particular form factor/config) to use that way. Everything else I've found is kind of nonideal in one way or another.