Curious to hear feedback from folks who have their car serviced at the local dealer that was purchased from a regional competitor. I'm looking at several at the moment and am leaning towards the competitor. However, said competitor is not at all convenient to drive to for service, etc.

I'm sure your mileage may vary based on the dealer but would love to hear any specific instances that made you regret going that route.

Since I'm likely to mod suspension and exhaust at a minimum, I'm thinking they will be less mod-friendly than if I bought the car from them to start with.

Or am I being too cautious with this approach?

i wouldn't worry about it.

also be sure to meet the right service advisor who is more 'mod-friendly'

i have three Pdealer near by but, luckily, i ran into a great guy at McKenna.

I've never purchased a car from my local dealer. In fact, I purchased my current car from a Denver dealer who had CPO'd it, then had to take it to my local dealer about 4 times to resolve PCM issues under warranty. They never complained, as they make money from warranty work.
Last week I took it to another nearby dealer for CPO warranty work and it went smoothly. But when investigating some squeaks and rattles for me, they quit when noticing I had aftermarket suspension. I doubt if would have been any different if the suspension had been installed by them or if the car had been purchased from them.
Go to where the best deal is.

I'm with you. Find a service advisor who is "mod friendly" There are many out there.

Up here in PNW, the deals are not great and dealers are hogging old model year as if they were gold, *cough* Barrier Porshce *cough*. So I just bought my CPO C4S from CA and had it shipped up here. After all that, it was still more economical than purchasing it from the local dealer. Since the dealer's service department gets reimbursed by PCNA for the warranty work, they should not have problem with working on your car. They might just not give you a loaner car or stick you with a cheap Enterprise rental instead of a Boxster, Cayman, or Cayenne V6