Looks like there are a lot of complaints about Eclipse look-and-feel under Ubuntu Unity (10.10 and 11.04). The main problem is that there are a few inconsistencies with default Eclipse coloring and Ubuntu system colors. Some interface objects have low color contrast, like tooltips and selection lists.
I’ve found a few solutions on the web to this problem, but none solved the whole problem. Some suggested to edit a file and force a color only to tooltips but this is counter-productive because tooltips are not the only object with color problems in this situation.
So, if you don’t mind having to change all colors in your Ubuntu, I’ve found out a simple solution to the problem. Install gtk-chtheme, open it and choose a theme that works better with Unity theme. I’ve found out that the Human theme works very well. 
$ sudo apt-get install gtk-chtheme
$ gtk-chtheme
See ya!
