There is nothing wrong with this approach, integration provides a great deal of comfort. There are environments, however, where a software-only model is becoming attractive. Virtualized server infrastructures can now run storage software as a service, many cloud storage infrastructures are running storage as an application on commodity hardware, and of course, there are the vendors that can run storage services on a standalone Intel server and add value to standard off-the-shelf storage.
However, you still need reliable hardware to run the applications, and if you buy hardware from the big three, they normally sell their own software to go with it. So what does this mean for software-only storage? That there is increasing room for storage vendors that are primarily focused on the hardware. These are typically smaller companies without hordes of software developers. They are building storage hardware systems, potentially adding basic hardware intelligence to the systems to help with performance or reliability and then providing this storage at very competitive prices. Combined with some of the software-only storage services, this makes for a solution worthy of consideration in more than a few data centers.
Clearly the do-it-yourself approach is not for everyone, and the primary storage vendors are not going to need to alter their strategies anytime soon, although I like the hardware-only option. However, in a cost per TB type of business, or one where storage performance is secondary to cost, then the storage services in software are very appealing. These customers need storage companies that are focused more on the hardware than the software companies that are developing cost effective, reliable storage systems.