I agree about the not wanting to become just anywhere, USA comment. But I would also love to see a Gap downtown somewhere. If you look at Kittery (all chains) and Freeport (all chains), you notice that one is anywhere, USA (Kittery) while the other is unique (Freeport), so I really think it is the form of the building stock, more than the use in that building, that matters. This supports the notion of Form Based Zoning Codes being able to contribute to the uniqueness of a place. Look at Trader Joes, they have all Portland themes in their store here. I think the true thing to avoid is the monotonous chain that is going to ruin things, not all chains in general.
One reason Five Guys may have been the only tenant to open up in that space is that the previous owner (local) was priced out by the landlord, at $5,000 per month the space is unaffordable to all but those who do business on a national scale, it would seem. I wouldn't want to set up a chain mecca in, say, Bayside, and have everyone come and go without seeing the Old Port (because remember the Old Port is our very successful answer to the Maine Mall's effect on Downtown), but at the same time mixing them throughout doesn't seem too bad of an idea. People are starting to move back toward cities, meaning their tastes in building stock are changing, but not their tastes in land uses (not int he stores themselves, that is), so it may be time to bring some chains back to the City, bit by bit, as the people move back.
Portlander -- Levinsky's? Please explain. I only remember them on the corner of India...were they on Congress at one point in the old LL Bean outlet before Bean's?
(PS - this burger joint, if open late, will be a welcome change to the only food available after the bars let out at 1am (pizza)).