The Bamboo is built for fun, and less detailed tasks. The nibs are
known to wear out quickly. Fortunately, you can
replace them on the cheap.
The Intuos comes with a few nibs, one of which is graphite, and imo, offers better control for finer detail.
It takes a bit to get used to using a tablet, regardless of which one you purchase. You just need to dedicate a bit of time and effort. Once you feel comfortable, you often wonder how you got along without it. But, they aren't for everyone, and some people find their work
flow is more efficient with a mouse.
As far as the scratching? This doesn't detract from the performance of the tablet, unless you're talking about deep grooves. The Intuos come with a protective sheet that covers the actual tablet, but not sure on the Bamboo. Either way, it's most likely nothing to worry about.
One thing to consider, is the fact that the Bamboo is not as pressure sensitive, and you may find yourself applying excessive force on the tablet with your pen in order to feel the level of control necessary for your tasks. This is obviously much less an issue with the Intuos, due to it's increased pressure sensitivity.
The Intuos are more realistic to tactile mediums than the Bamboo, and therefore also take less time to feel comfortable using. My first tablet was the Graphire line, which is what the Bamboo replaced. I felt very awkward using it, and gave up quickly, but when I got the Intuos, it felt more natural, and the difference was very noticeable.
I seriously think that if you can afford to purchase the Intuos over the Bamboo, it's a wise choice. It's better to spend a bit more on something you'll actually use regularly, than to spend a bit less on something that will quickly become a dust collector.