Residence Inn Garden Grove is my favorite after the Villas @ the Grand Cal. (I've stayed at pretty much every Marriott w/in 5 miles of the park because I build up a bunch of Marriott points that I need to use & my family likes the Mouse!)
In my opinion it has better customer service than the RI Main Gate and better beds. You can take ART. It is somewhat of a hike. Looks closer that it is -- I did walk it one day -- thought it would take me 20 minutes, took my 40 minutes -- wasn't feeling all that well, so might not have been a fair comparison.
The buffet breakfast is good -- standard fair if you are used to Residence Inns -- usual hot section & cold section. Larger buffet area and seating area than RI Main Gate.
It's also closer to El Pollo Loco than RI Main Gate. We usually like to get some crazy chicken for a budget meal because it's so darn good & reasonably healthy -- we can't get it at home. It you've never had it -- you should give it a try. Get 2 - 3 pieces of chicken per person, plus some sides. They'll give you tortillas. DH usually grabs it while the kids are resting & I'm catching up on some emails/work, then we eat & head back for more rides.
My general rule of thumb -- If you are staying off property, the farther away you get from the park, the better customer service you'll receive. I haven't stayed at HOJO's, or some of the other DIS favorites, because I have all these Marriott points & and my DVC points. So, it's either Grand Cal Villas or RI Garden Grove. If for some crazy reason, that isn't available, we'll stay at the Courtyard right there.
But we really prefer the kitchen. It's nice to be able to put water bottles in the freezer. We will sometimes make rice krispy treats. We also like having a place to put leftover take-out & make pop-corn. Courtyard has a mini-fridge, but doesn't have the buffet breakfast.