"The world is flat."
I'm not sure I believe this one. I've lived in a lot of different places...and I know that I build better technology when I'm surrounded by technology people. Humans are social animals, and if your peer group is building next generation technology you're more likely to do the same...likewise, if your peer group is pushing paper, building cars, milking cows, packing chicken, etc. I suspect you're far less likely to be producing the best technology. You might be happier. You might be able to run your company for longer without raising money or running out of what you did raise. But, I doubt you're building the best technology you're capable of building. Maybe I'm unique...maybe nobody else is effected this way, but I doubt it.
Of course, if by saying "enterprise software", you mean "a market no one else is interested in, and thus I can build any old technology I want and people will have to buy mine", then sure. No matter where you are, you'll do fine. But what happens when an agile web-based competitor arrives who are using modern techniques and have hired the best nerds they could find in the technology center where they're based (which are, let's face it, better than the nerds you can find in a non-tech-focused city)?
I also have very little data, I just think the reasoning is flawed somewhere, since whenever I've met someone starting a company in the sticks (often "to save money"), it is fatally flawed from the get-go--often based on five year old thinking. I'm just suggesting that maybe there is a continuum of "tech productivity goodness" and that the Valley is near the top and Idaho is near the bottom, and placing yourself at the bottom of the continuum might be bad for your odds. Balancing other elements is certainly fine...but beware of what you're giving up by "saving money".
In my previous business I did a lot of work in out of the way places ("packing chicken" was actually true of the city where I once worked on a pretty big project, and the IT and software managers there were desperate for talent but simply couldn't hire it at any price)...you keep acting as though "once you have your employees" it doesn't matter where you are. But, employees leave, and if you're lucky your company will grow. You have to hire sometime if you survive.
I'm not saying you're wrong, but I think the evidence is much stronger that you are than that you're not.