Frustrated -
My guess is that Microsoft is fanatical and a little schizophrenic about storage is because they are a huge consumer of storage.
My organization utilizes Windows Storage Server, primarily for Storage, backups, and static data. We don't use it as an iSCSI data target for Exchange but have explored it with Dell and HP. We don't use it as a target for vSphere but use some mid tier SANs with appropriate drives and RDMs configured where possible.
My understanding from my Microsoft rep and the few times I have been invited into the Microsoft technology locations, a lab my organization used in North Carolina, and the Redmond Executive Briefing Center (hint - it's not limited to executives), I have seen dozens of different vendors including all the major SAN vedors. I used to work for a major hardware manufacturer and I believe we had about 300 people assigned to Microsoft including disk specialists to include SAN as well as server chasis based storage.
From what our Microsoft TAM says the Hotmail and BPOS solution track drive failures down to the serial number, lot number, and work with the drive manufacturers on a monthly basis. They won't provide us any numbers or manufacturer information no matter what our lawyers agree to sign to swear us to secrecy but apparently have worked with drive and chasis vendors to improve their products.
Exchange 2010 has allowed us to use cheaper storage; $150 for a 2TB SAS 7200RPM drive instead of $900 for a 15K 2TB SAS adds up after a few drive array enclosures. No, we haven't taken the SATA jump or DAS jump for Exchange with an all-in-one server but that may be next if we can prove it would be cost effective. We love the flexibility Hyper-V and VMWare provides and once Hyper-V R2 SP1 has memory overcommit we may cut our VMWare maintenance investment. The blocker for the AIO servers are the HLB requirement to load balance the AIO servers because of the CAS role.
Thus, I reiterate, Microsoft seems fanatical and a little schizophrenic because they appear to be a huge consumer of storage even though they have never manufactured a single disk. They also write the software which resides on these industry standard disks.