Well, today I sold my car and bought my bike. I wound up getting a Gary Fisher Simple City 3, made by Trek:

2010 Fisher Simple City 3 - Bike Archive - Trek Bicycle

I really like this bike. It's got everything I need. It has a Shimano 3-speed IGH, which I definitely prefer over the single-speed I looked at yesterday. It does have a coaster brake in the rear, but it also has a front caliper brake for emergencies. I really like that I don't have to worry about the hub and rear brake gumming up. I'll be able to shift and brake regardless of weather, which is subject to change minute-to-minute here in Florida. It also has fenders, a chain guard, and a front rack and basket(not mentioned or shown in the Trek link above). Saddle and bar are comfy.

I got the bike new for $640, after tax. I may have been able to find a better deal at one of the other shops, but I'll be passing the Trek dealership everyday on my way to school, and it's also the closest shop to my home. So, future convenience factored in here. I should easily get two or three years out of this thing, long enough to plan and save for my next bike.

Interesting choice of bikes. Hopefully it will treat you well. It seems to have a lot of good compromises.

5 miles is a moderate commute. Not long, not short.

I am a big fan of toeclips (or clipless pedals, but for a daily commuter, I'd go with plastic toeclips & street shoes).

I was going to suggest also keeping an eye out for good used bikes. Or, perhaps a good used "road bike" will be your +1 bike sometime in the future.

Riding miles with a heavy backpack is not recommended.
Get a bike with threaded eyelets for a rear luggage rack. Pick a suitable rack and fit some modern panniers with quick-release locking hooks. Make sure the rack is compatible with the hooks. A lot of rack makers do funny things, you need simple round section lengths for the hooks.
Avoid suspension.
Fit bolt-on fenders
Upgrade the tyres to a reliable commuter style with good protection.
Those drop bar, disk brake cyclo-cross/touring bikes are neat but at your price bracket, a simple hybrid style is better value.
Giant Escape City is fully equipped and a good price.

You must have missed the thread where the OP posted that he got a bike already, and included a link to it.

I like it, what's the top speed specification?

First, congrats for making the first real commitment (getting rid of the car). There will be days that you wonder if you made the right choice; you did!

Next, I would recommend a rear rack and a wald basket. It makes the bike significantly more practical. Further, it gives you a place to put your backpack when you tire of wearing it. The only other thing I would recommend is checking out Amazon and getting some lights. Both of these recommendations relate to life as a college student; however, they are applicable to any commuter.

As far as the bike itself, it looks like it will suit you well. Just make sure you remember to pack a small air pump and a patch kit, and have some chain lube at home.

give the guy a break on the speed thing...and to be fair there is something to what he says...not so much about the bike itself...moreso about the gear ratios...

for example, the bike he bought, let's assume it has a 42t chainring and he is capable of maintaining a maximum of 120rpm on his pedals, then the max speed he can produce on the 3rd gear would be 30.7mph...but if he were to put on a 22t cog instead of the factory installed 18t then it would only be 25.1mph...so there is a real difference in what is physically possible given a specific gearing...even if he can do more rpms, then the logic still follows...just at higher speeds