At the minimum, you should give users a choice to select the look-and-feel such as you get with Firefox 6.0, where if there is more text than the window size, the scrollbar is shown ***all the time, and has good ***contrast color so it is highly ***visible.

I am not a game player, I am a programmer. There are three most common things I do on my computer. One is searching for files. Two is programming within some IDE. Three is trying to find bloody scrollbars. In fact, I estimate I am looking for scrollbars about 200 times per day. Yes I can understand that real estate is limited on the screen. I measured several of my windows and found out that typical width of a window is 150mm, and the height is 100mm. The vertical scrollbar if it were always visible take 3mm width and 100mm height. Horizontal scrollbar would take 3mm width and 150mm length. So the two scrollbars have area (3*100 + 3*150) and the window area is (150*100) so the ratio is 750/15,000 = 5%. So by making the scrollbars invisible you saved 5%.

To put it differently, I have to hunt with my mouse over the edge of the window repeatedly until I can see the invisible scrollbar. To put it yet differently, it is very bad idea to try to save 5% and making the window unusable because I can’t find the bloody scrollbar.

Again I have great deal of respect for all the Gnome programmers, but please give user an option to see the scrollbar all the time if there is hidden text in the window and make the scrollbar highly visible by providing proper contrast. It should require very little code since persistently visible scrollbars are easier to design. Use the look-and-feel of Firefox 6.0. I am so desperate that I am looking into installing xfce or KDE.
respectfully
-jim

Regarding the overlay scrollbars, it is most annoying that the overlay appears only when getting close to the indicating vertical bar. So it requires to navigate the pointer to that tiny vertical bar, rather than simply move to the right border of the text area. This is difficult and slows down work a lot.

Devices with touchscreen are fashionable now, and touchscreens might become standard also for notebooks used to work rather than just play and surf around.

So I am pretty much against this new fashion of overlay scrollbars. It should at least be easy to switch them off, but better be discarded as it is one more step on the way to unfunctional notebooks (just as the move from 4:3 to widescreen was – also driven by movie consumers but not professional users).

However, it may be good with a touchsreen and well-engineered trackpoint combination but without a touchpad. Or allow the touchpad to operate as large 2D scroll-control (and nothing else).

If you want to ape Andrdoid or IOS, please do it properly.