In the past, I've been highly inconvenienced when I've mixed and matched products and services from different vendors. So much so that I now avoid it by paying a premium.
To put it in perspective, consumers do not buy a car from one manufacture, the engine from another, and the service plan from, yet, a third company. Too much finger pointing. While the upfront cost may be less, the TCO is only cheaper if your time is worth nothing and you never have a problem.
I've gotten a little aggravated over the past few months when I've seen friends, who've paid good money, only to be given the runaround when there's a problem. Frustration results when reality is not in line with expectations. The one thing everyone has at the top of their list is to have their day run smoothly and being bounced between different companies with mediocre customer service is an unnecessary distraction.
You can probably read between the lines as to what I'm talking about.
Whew... now I feel better.