Here's a great post from another member explaining the technology:
I wanted to comment on the confusion around the PenTile display in the overall thread. What some refer to as "pixelation" is actually something a bit different. PenTile technology uses 2/3 the number of subpixels to render each pixel, which saves power while also producing a brighter screen. What people call the "screen door" effect or "pixelation" is actually pattern visibility. In certain color combinations the patterns created by the subpixels become visible -- green on black is a common one, which you can see in the battery indicator of the notification bar. Some people are distracted or annoyed by the patterns, while others can hardly see them or just ignore them. Personally after using the beautifully crisp OG Droid screen for almost 2 years, I was afraid the PenTile screen would put me off the Bionic after reading about it. However, after seeing it firsthand in the store and now after a week of owning it, I can say it doesn't bother me one bit. I can sometimes see the patterns but they don't distract me, I basically just "look through them" and they disappear. For some people though, it's so annoying as to be a dealbreaker. I would highly recommend for anyone considering the Bionic to take a look at one in person before deciding. It's highly subjective.
One thing I am sure of though is the power savings. On my OG Droid, Display was always #1 in the Battery Usage Stats screen, often as high as 90% of total battery life. On the Bionic this is reversed, with Display only using about 10% of battery life. Of course, this is offset by other power-hungry components (4G radio, I'm looking at you) so overall battery life is in the same ballpark (although I'm still getting somewhat better battery life I did with my OG Droid).