The great advantage touted for these things is readability in all light conditions. As we all know, conventional screens on phones, tablets, laptops, netbooks and other performers in the mobile device circus often become nigh unto unreadable in bright sunlight. Conversely, a purely reflective display in a dim room is equally unreadable. The transflective display can operate both ways and adapt.

I'm also interested for another reason. One reason I've resisted ereading is that I HATE doing pleasure reading or reading of a lengthy document on a backlit screen. It's funny - I'll do interactive stuff on a computer all day without complaint, but I do NOT want to read a novel in glowing text being pushed into my face. Thus, I'm not about to read books on a tablet with a normal backlit screen. If I'm willing to spring for a tablet, I also can't justify buying a special purpose "ereader" with an e-ink display. I'm hoping that I can eventually get a decent tablet with a transflective display. An early entrant, the Notionink Adam, looked interesting, but seems to have some serious drawbacks and quality issues according to reviewers. I'm watching for these displays to mature, as they start appearing on mobile devices.

Anyway ...

I bought myself a new GPS unit for hiking - a Garmin Oregon 550, which touts its "transflective color TFT touchscreen". My purpose here is not to review that device (I like it - leave it at that). I'm just going to compare the screen against my smartphone screen, an AMOLED display on a Samsung Epic 4G from Sprint(rebadged Galaxy S). This is generally regarded as a good display - bright and sharp. Can give the iphone displays of the same vintage a run for their money.

To be fair, the Smartphone display is twice the linear resolution and somewhat larger:

That's not what we're comparing here. We're interested in the visibility in indoor/outdoor light conditions.

Both units have their screens set to max brightness for these photos. Since the Garmin GPS is "transflective", you can read it without the backlight on.

Direct Sunlight, Garmin not backlit Impossible to get a picture without reflection off the glass. DOES illustrate that you can read the Garmin's display and it's pretty much impossible to see a bloody thing on the phone screen. In direct sunlight, there's not much visible difference between backlit and not.
Outdoor shade, Garmin not backlit The phone is much brighter, but you can still read the Garmin display. Presumably, this means the Garmin isn't drawing as much power for the display as it would backlit.
Outdoor shade, Garmin backlit The phone is a brighter display, but they are closer now. The picture is darker overall because of this. The important thing is the relative comparison of the two screens.
Indoors, Garmin backlit Fairly dark room (blinds drawn). Both readable. Phone, again, is a brighter display. Taken handheld without flash, so it's a bit fuzzy, and the actual units don't show up, only their screens.

Overall, I find it encouraging. I still want to get my hands on a tablet with a transflective display to check it out, which means "read a book on the thing in direct sunlight".