Commuting - Help me toughen up my commuter

I have been into mountain biking for a while and use to use my mtb to commute to school. I just won a brand new 2009 Jamis Sputnik in a raffle. I'm stoked about it. The SS was a challenge the first few days on some of the hills, but I'm zipping pretty good now. I have been using the Sputnik as a commuter (5 miles each way). I love reading about everyone commuting by bike to work and just want to be one of those guys.

I'm use to mountain biking and being able to ride over anything I want, but I realize these skinny wheels and tires are a bit fragile. I was cruising downhill the other day coming up on a place in the sidewalk that I know had a raised block of cement. A person got in my way and distracted my and I hit that raised cement pretty good--double pinch flat.

I see all of you raving about those Surly Cross Checks. I hadn't considered a Cyclocross before, but it seems like a good idea. There are a lot of dirt trails around and I like being able to ride in the grass for a second or off a curb if need be. Do you think I could just pop some cyclo style wheels and tires on this bad boy? Thoughts? Recommendations?

I added a mirror as everyone has recommended. Other than that, she's bones stock. I've been reading all over these forums like a madman and think i've picked up some of the general commuting concerns. Any thoughts or suggestions for this bike? I really like its style, but might need a bit more toughness/usability.

Can you fit a wider tire on there? That's where I would start, - and probably finish.

Make sure the tires are inflated to the proper PSI to avoid pinch flats. I ride in grass and off curbs on my 23mm tires all the time FWIW. I'll ride in gravel and on fire roads too if need be but yeah, not the best bike for it.

I don't fly off the curbs at 20 mph mind you but I certainly don't get off the bike or ride a block out of my way just to avoid going off a curb.

The most you would have to do is get a stronger rear wheel, and you should only do that if you are breaking spokes constantly. Few people have trouble with front wheels, so that is probably fine being left as stock.

To avoid pinch flats do not ride with low air pressure. The only way you could ride at low air pressure while avoiding pinch flats would be if you were to buy tubeless tires and wheels, or tubular tires and wheels, both of which are expensive options. Just keep the air pressure high and you should be fine when it comes to pinch flats.

I use 28c tires on my fixed gear. I never pinch flat, but I try to stay on roads and MUPs. I also try to pay attention if I'm going over a curb: wheelie over with front wheel and unload as much weight as possible as the back wheel goes over. Even so, I have gone up and down curbs without issue, and hit three sets of railroad tracks at the bottom of a steep hill with no flats. The tires are Continental Ultra Sports that suck up every little bit of glass and debris that I come within a mile of (I hate these tires), but they never pinch flat. I'd just go with the widest tires that you can fit in the frame (and under the fenders if you use em), and try to buy something of decent quality. Then just pay attention to what you're running over and keep your tires pumped up.

If you are riding on the sidewalk, pedestrians are not getting in your way; you are getting in their way.
You can ride road bikes over rougher terrain but you have to learn a more responsive style of riding. MTBers, esp with full suspension, never really learn to finesse the bike over obstructions, they just charge through them. With experience, you will learn how to automatically unweight the front of the bike without even thinking.
The only time I have smacked my front wheel hard was riding a fully loaded touring bike down a very narrow winding land. Aroubd a blind corner the wheel fell into a deep pothole and I didnt have time to lift the front. Fortunately the handbuilt 36 spoked wheel survived intact.
The Sputnik has standard 32spoke wheels which should be very strong.
Wider tyres at high pressure can protect your rim from damage. The Sputnik may take 28mm but these vary a lot in actual width.