Should I get a road bike? Last year I started biking again. My current ride is a quite good "cross" bike weighing a bit more than 10kg  (~22lb, I didn't weigh it). Currently I'm doing around 200km (~120 mi) per week, mostly on roads. Now I'm wondering whether a road bike would be beneficial for day-trips or such. I live near the Alps in a hilly area.


Is there a notable benefit from the lower weight of a road bike? (I weigh 80kg, 175lb) Unless it's a really step difference or a I pay a lot for a very light bike I don't expect much benefit, but might I be wrong?
I wonder how notable road bike tires might be, I'm expecting way less resistance. Any way to qualify that?
A road bike handlebar has more ways it can be gripped, which might be comfortable on longer rides. 
A road bike looks nicer :-p


Are there more important factors I should consider? I'd certainly keep my current bike for times where I have to carry luggage or want to stay off roads.
It's all about having the right tool for the job. Road and touring bikes are designed for long rides on roads. In contrast, mountain bikes are designed to go off road, and hybrids are designed mostly for casual riding. If you're doing 200 km per week, you're serious enough about cycling to notice a serious difference when you switch to a road bike.

I recently made a similar switch. I was riding a mountain bike, which I used for commuting, off-road trails, and road rides. I eventually found that I was only spending about 10% of my riding off-road. I considered switching to thin slick tires, but it was obvious to me that I also needed more hand placement options, a more aggressive riding position, a higher maximum gear, and lighter weight. In other words, I needed a road bike. When I sold my mountain bike and got a road bike, I instantly noticed a 2 to 5 kph speed improvement for the same effort.

Since you're considering switching from a cyclocross bike to a road bike, you should expect a less dramatic change, but if you feel like you're losing out from using the wrong tool for the job, you might as well try a road bike. You could at least rent one for a day and see how it feels. Alternatively, you could consider switching just the handlebars and tires on your current bike, since it sounds like you already have a light-weight frame.