Thought I'd reply before reading everyone else's post. So, these are just my opinion and why I shop how and where I do.
- large selection of dog food products - pre-fab or raw frozen. That is, would you choose your pet store by who sells the brand that you want or would you be open to other brands if the store offered other "attractions"
I go to the pet store that carries my dog food. And since you know all about how hard it is to find a good food, them carrying the food I want would be my "main attraction"
- price - I'm asking here about buying at the grocery store vs. a pet store.
Where do you buy your food currently.
I buy my dog food at a pet store. And I'll pay whatever I need to, in order to get the food I want. Meaning if I have to pay a ton for Orijen, I will. I'll just eat cheaper things. Dogs come first. lol Don't they? j/k
- location - how far would you drive
If I could get everything I wanted in one place, I'd be willing to drive 30 mins. Take into consideration that I live in a metropolis, so driving more than that for a pet store isn't realistic. We have too many where we are.
- shopping experience - do you expect trained and knowledable staff to help you make a decision?
Yes. It's the biggest reason for why I shop where I do. Most of the employees are pretty knowledgeable about most things. Food, not so much, but I don't expect them to do the type of research, say, Ashley does 
- for unique product (e.g. leashes, collars, grooming supplies, speciality items) are you more likely to shop online or check your pet store first. How satisfied have you been shopping for these items at your pet store?
I do check my pet store first. Unfortunately, it typically costs a lot more than buying online. But when I need to see something first, I will usually end up buying it there, if it's under $50. If it's over, I'll check it out in-store, then buy online.
- how interested would you be in a store that offered pet supplies, as well as grooming and dog day care, or even a dog cafe?
I personally wouldn't want any of the rest. The groomer would scare me, I have a good daycare/training center, and I live in CA, we can go to a lot of outdoor eateries and have dogs with us. BUT, this is where things matter. 1. If you had a good groomer, who knew all kinds of dogs, and how to handled them, I'd probably go. i.e. if they can cut your pups right, then I'd go. Daycare, obviously it'd have to be a smaller place, so you'd most likely cater to smaller dogs. There's a lot that goes into daycare, the people who work for you, their qualifications, if they understand dogs body language, etc. Dog cafe, I guess it depends on what you have. OH!!! My pet store, has a pharmacy. That may be something else you can do.
- given the aging baby boomers with disposable income is there a market for "high end" pet experience?
I think this would depend on your area. Where I live, ohmigod, paying too much is almost a way of life. We have this one independent pet store, everything in it is always overpriced. What costs $10 at my store, can cost almost $15 there. But, they have a ton of cutesy collars, leads, and clothing. It's focused more on people who pamper and dress up their small dogs as accessories. Think Paris Hilton.
As you know, no matter what you open, you can't make everyone happy. For myself, I wish pet stores around me carried more agility stuff. And I don't mean equipment. Almost every single item I bought for my trials....I bought online. Because either no one carried it, or they charged twice as much. My main pet store....I go to because of their HUGE selection of "not PetCo/Smart" dog foods they carry and HUGE selection of "not PetCo/Smart" treats that they carry. I try to buy everything else there, but sometimes, PetCo/Smart just has what I need.
I hate to say it. But I go to PetCo for specific things, I go to PetSmart for specific things, I go to my independent pet store for specific things. Because all 3 carry different things. So confusing! lol.
One last story. My friend's friend opened up a pet store near my work. I was debating on checking it out. But sadly, I thought to myself, "what kind of idiot would open up a small store....a few blocks away from one of the biggest independent stores in town?" And I decided I didn't want to go anymore.
Sorry for rambling on and on. Although there are probably a few dozen pet stores in a 30 mile radius from me, not one store has everything I want. But that's okay, everyone has to have their niche. I say, figure out which one you want to be in, see what's in the area, what people want, etc. Like I said, living in SoCal, we have a lot of frou-frou shops that charge and arm and leg, but they do well, because the rich folk think it's a "boutique" and LOVE it! lol.
After reading what everyone else said, I'd have to say the variety of treats is also what brings me back to my store over and over again.
And now that I'm reading all this....I'm thinking online and catering to the "sport" dogs (which includes show dogs). Need to figure out how to start that company. One stop shop for those doing obedience, rally, showing, and agility. lol. not to mention flyball, dock diving, and tracking. Hmmm.....
Dangit, one more edit. As for advertising, as long as it's okay with the franchise, don't forget about all those "coupon" places. I know here, we have Groupon, LivingSocial, SuddenValues, etc. Not sure what they have up there, but it's a good way to get people out to the store (once it's open).
