This bike is unlikely to be any faster than a comparable mountain bike because of gearing. While it may have more gear combinations, the overall range is probably quite similar. And in any case, you are unlikely to run out of gears on any bike you buy. (In other words, if you rarely or never use the big chainring/small cog combo and wish you could still go faster, then you aren't really using the highest gear you already have.)
What makes a bike faster is basically (1) slicker, higher-pressure tires; (2) less weight; (3) better aerodynamics; (4) a stronger rider.
The Navigator will come with "semi-slicks," tires that are smoother in the middle than MTB tires. That will help a bit. The Navigator will weigh somewhat less than a Huffy, which will help a bit more. Your riding position will be just as upright, if not more so, giving you no help on the aerodynamics. And the rider is the rider. All in all, don't expect huge gains in speed, although just having a lighter bike that's properly assembled and lubricated and built from quality parts will make the whole experience a lot more enjoyable.
Comfort bikes are mountain bikes with "comfort" features. The suspension fork, the suspension seatpost, the big fat tires, the adjustable stem, the plush saddle, the very relaxed, upright riding position -- these are all things designed to reduce impact on the occasional rider. They sacrifice speed for comfort. They add weight, and they bleed off rider energy (some of your pedaling effort gets absorbed by all those springs).
The sad part is that they often end up being terribly uncomfortable for riders who get into it, wanting to ride more and farther. The riding position is rigid; after a while your back and arms start to hurt because you have no other way to sit, no alternative posture or hand position. The saddle is so wide and soft that it chafes, causing saddle sores, and compresses your soft tissues, causing numbness.
There's a reason roadies ride the bikes they ride.
Still, drop handlebars are non-negotiably "out" for some people. For them, some of the "flat bar road bikes" now hitting the market are an interesting alternative. At your Trek dealer, ask about the 7500FX and 7700FX as examples of the type.
The 700c hybrid and the 26" comfort bike are starting to become indistinguishable from each other in many manufacturers' lines, partly because the benefits of the 700c hybrid are better realized with these flat-bar road bikes. But still, if the 7500FX type bike is still too aggressive for you, you might want to at least look at the 7200, 7300, 7500 standard hybrids from Trek. Because they come with somewhat narrower, higher-pressure tires, they are at least a bit more roadworthy than the Navigator and its ilk.
Most major manufacturers -- Raleigh, Specialized, Cannondale, Giant, Jamis, Fuji, etc. -- offer competitive models. I cited the Treks only because you were already looking at one, not because they're any better or worse than the others. At this level, the quality of service and support offered by the local bike shop is a more important distinguishing factor in a purchasing decision than the bike itself is likely to be.