Ultimately, I think every vendor will have customers with good experiences, and customers with not-so-good experiences. Without sufficient data, it is hard to say which vendor, in general, does a good job for their customer base re: TAC.

What I will say, albeit anecdotally also, is that TAC experience with the vendor will often be good if you have access to an SE on a regular basis (i.e., one or two in your country of abode). It will even be better if that SE is naturally diligent. Which means that oftentimes, it will come down to one person, to give you a sense of how well a large organization like an OEM treats your business. And if that one person were to leave and move on, the gorilla that is the OEM could come crashing down on you in ways you didn't think was possible.

So yes, while it is possible to institutionalize processes and such, like with everything else in life, your experience is very likely to come down to one or two people that care deeply enough to (want to) make a difference.

For me, if I have ever have to have a relationship with a vendor, it is a priority that I establish a close relationship with someone on their sales and engineering team, as that will determine how much support I get if I ever run into trouble. And OEM's that were once great at this can quickly become the worst you've ever seen, if those two people were no longer there or stopped caring. In other words, there are no forever-guarantees, and it comes and goes in cycles.

Mark.