I just don't get the JBOD part... Every time I see this as part of Exchange 2010 literature I cringe a little bit. I totally get driving down costs and cheap SATA drives (use them myself in many scenarios) - but they are SO cheap and SUCH a small cost compared to the rest of the server, why not spring for a second drive? At the VERY least the mirroring built into the OS will save you a lot of time in rebuilding the server in case of drive failure - and an inexpensive $50 raid card makes it even easier (or just use built-in raid 1 on the mobo depending on the box you're using). JBOD just seems a bit irresponsible given the low cost to implement raid1 and relatively big payoff in case of drive failure...
Otherwise, great article, thanks!