Yes, IBM does (mostly) work best with other IBM stuff.
There are certain areas where IBM just doesn't quite grasp the whole picture yet, prolly never will.
I won't hesitate to use 100% IBM, but that is because they do such great and thorough jobs at "Deals" and Kits.
Where I draw the line, is when things in IBM are fixed with a hack in the OS Department and a Bad soldering job on the "hardware" end of the problem. Rather than just fix the real problem.
When I begin to see this, I call the bluff. Sometimes IBM bawks at a balk. If that happens, EMC gets a call.
If IBM fesses up, they get much berth to fix the problems. If they don't show honest efforts, I start scheduling sales people to show up during the time the engineers are around trying to fix the problems.
It is amazing how much sway an engineer can have with a company sometimes.