My biggest problem with UPS is the fact that, just a few years ago, no matter what I ordered and from where it was shipped (within reason, of course), I would get it within a couple of days pretty reliably. I never had to spring for "2-day" shipping at an additional charge. Now, if I don't pay for it, it's a pretty safe bet that I'm at least a week out from receiving my package, even if the merchant with whom I place the order is within 200-300 miles from my home.
The cynic in me wants to think that they intentionally delay standard ground packages in the interests of promoting their faster shipping services. In truth, it's more likely just a side effect of the phenomenal increases in on-line commerce over recent years.
That said, I find UPS and FedEx fairly interchangeable for my shipping needs. Sorry to hear you don't see the same in your area. I would bet good money that a few well-placed bits of feedback correspondence to UPS would make a big difference. That business is just too competitive for them to turn a blind eye to poor performance by any part of their delivery chain.
As far as your experience with GM goes, yeah, they probably could have handled it better. The first rep who replied obviously had something that incorrectly indicated you selected a different delivery method. The second rep must have figured that there wasn't much to be done about it at that point, but you're right in that they could have been a bit more understanding with your complaint, at least offering a refund of any upcharge for FedEx shipping if there was one.
Sounds like you received your package ok in this particuar instance. I'd say if this is the worst you're treated, and if it's not typical of their CR responses, then I wouldn't get too worked up about it. On the other hand, it would certainly support a decision to take your business elsewhere, if there are other service deficiencies commonly experienced.