I used to tour on and off road on a Giant Boulder MTB, and commute on one. I sold it because the frame was a bit small for me and replaced it with a Giant Rincon MTB with a larger frame.
The Boulder model is good strong bike, and you shouldn't have any problems with it. However, for commuting, if you decided to fit racks and panniers, the chainstays are a bit short so your heels may strike the panniers. I used smaller panniers and adjusted the rack up and back as far as possible.
I also found that the really knobbly tyres don't grip wet road very well, so I changed to a semi road trail tyre, and also fitted some cheap clip on mudguards.
For commuting to work, I'd recommend:
1. Good wet weather gear, including shoe covers or boots
2. lights, as many as possible
3. rear vision mirror (Highly Recommended)
4. if your panniers etc aren't waterproof use large garbage bags inside them
5. Lots of bright clothing.
(dealing with cars)
7. Mounting bracket for above.
The other thing to check with the Boulder is the gear change mechanism. If you have to wear gloves on really cold mornings, can you shift those tiny little levers? It's only my opinion on the gear levers, as I don't like them.