If I bought a bracket like that for every drive I use, that would entirely negate the savings from buying the 2.5" drives in the first place.
My biggest needs right now are for low-cost builds (~$350 desktops) and to replace ailing 5-year-old drives in my classroom machines. In either case, low-cost is a bigger demand than anything else.
As an off-topic aside, I don't see any reason to upgrade my five year old classroom computers. They're completely fine all the way around, and I expect that they'll continue to be fine if my company makes it to the point where we start dealing with Windows 8. Two cores and 2GB RAM are just fine for day-to-day work, even when the classes use virtual machines.