Poguemahone

You should ride 'em. Ride some you haven't been told about or considered as well-- you may be pleasantly surprised. Fit of a bike is largely subjective, and what works for one person don't always work for the next. If the store won't let you take a longer test ride, I'd offer to leave them a deposit, and if they don't take that offer, go find another shop. I'd ride at least the five miles you plan on doing daily for a test ride.
Unless the roads in your neighbourhood are in really bad shape, I'd ditch the suspension fork. That's a personal thing, and I'm quite sure someone will be along to tell me what an idiot I am, but on paved roads they're just added weight and cost. Also, be aware that different tires can substantially change the ride of a bike. Knobbies, commonly sold on "mountain" bikes, have a very rough ride. Slicker tires are used for pavement-- the tires on my beater "mountain" bike, which has never been off road, have no tread. This makes for a much smoother ride on pavement. Also, be prepared to change out your saddle if it really bugs you (you'll have some sore butt for awhile, so give a saddle some time, but if it persists, consider changing the saddle out).
You'll want to make sure the shop you buy from has at least free basic adjustments and can help you with a maintenaince schedule. You can do a lot of simple stuff yourself-- cleaning the chain and cogs, etc.-- without much trouble, but unless you're prepare to immerse yourself in the finer points of maintainence, it's best to have a shop do it.