The last time we used Mears (the old DME) was 1998. I have used a transportation service ever since. I think it is worth the $130 investment:
1. Eliminates the chance that DME will start the vacation off on a bad note
2. Use the free 30 minute shopping to get snacks and such (saves me more than $130 if same items were bought on-site!!)
3. No worries about return trip
I figure that I have already invested $$$$ in WDW, what's another $100.
PS - the kids get a really big kick out of a limo ride. makes them feel important!
The part of your post that I highlighted in bold is one of the best reasons to use a car service instead of DME. Your kids think the limo is cool, and that alone is probably worth the price.
But I take exception to your assumption that DME has a higher likelihood of starting your trip off on a bad note than a car service would. Since you've never used DME, you can't speak from experience.
DME is run completely differently than the old Mears service was. Disney sets all of the policies and procedures for DME, and Disney is known for excellent customer service. Mears does NOT have a good reputation for that. So even though Mears owns the DME buses and Mears employs the drivers, it's all done with Disney running the show, so things are VERY different than they used to be ... and I speak from experience.
Just as there is a sprinkling of bad DME experiences in board posts, there's also a sprinkling of bad car service experiences in board posts. The complaints pretty much cancel each other out -- problems are the rare exception, but they occur in both modes of transportation, not just DME.
As for saving money, I always get a grocery delivery. EVen if I rented a car or used a car service, I'd opt for the grocery delivery over the grocery stop. I've done grocery stops in rental cars on numerous vacations elsewhere, and each time I always wished I could have ordered the stuff ahead of time and had it delivered to my hotel. I'm just not a fan of navigating a strange grocery store and then waiting in line, when I know I can have the stuff waiting for me. I'm also not a fan of delaying myself rather than just getting to my hotel already.
Okay, forget the grocery delivery thing ... let's say you DID buy your grocery needs at your resort gift shop. Honestly, I don't mean to argue, but are you honestly saying that Disney marks up items so high that you would spend at least $130 MORE at a resort gift shop than at Publix??? In other words, you are saying that, for example, when you stop at Publix you buy about $65 or $70 worth of groceries, and that each comparable grocery item would cost 3 times as much at your resort gift shop??? Because the bill at the gift shop would have to be about $200 for you to SAVE $130 compared with buying off-site. You're saying, for example, that Disney resort gift shops charge $9 for a half gallon of milk instead of $3 at a supermarket ... or that a $2.49 bag of Doritos goes for $7 at a resort gift shop ???

Maybe you just made a typo, I don't know ....
You didn't mention whether you thought using a car service with a grocery stop would get you to your resort faster than DME (maybe that's one of the things you were alluding to about a "bad start" to the vacation?). If you
are thinking that, I can't agree with it. A car service without a grocery stop should get you to your resort in about the same time as DME. The trade-off with DME is not having to wait at baggage claim. If you add a 30-minute grocery stop to the car ride, I can't imagine that even on a bad day that your limo would beat other people on your plane to your resort.
So in ending, I'm not saying you should try DME. I think it's cool that you found something your kids and you like so much, and it's cool that you can afford to spend money on something that makes you happy. I'm just commenting on your negative view of DME even though you've never tried it, and your assertion that you SAVE $130 by making a grocery stop, implying that Disney's resort gift shop prices are about 3 times that of area supermarkets.