Is that a mountain bike, or a hybrid? Generally, in that price range, most mountain bikes are sturdy and reliable. The key to enjoying a bike is getting a good fit. If your bike shop is taking the time to make sure you get the size that fits you the best, and helps you "fine tune" the saddle height and bar height, you will have a good bike for rides of ten or twenty miles.
If the day comes when you want to go on a hundred mile ride, you will probably want a lighter bike, with slimmer tires and rims. But, even if you later buy a road bike, a mountain bike is great for everyday riding.