I would also slightly disagree with your comment that screen protectors degrade screen resolution, turning VGA into QVGA. That’s not been my experience. What I did see what a slight loss of brightness as the additional plastic layer absorbed a little of the light. Given the brightness of the screens these days, that 5% loss is not significant compared to saving the screen from scratches.

I extensively use my PDA as a GPS in a car. I wasn’t happy with the Axim because of the screen brightness - it wasn’t bright enough to see under the bright sun, and wasn’t dim enough to drive comfortably in the night. The iPAQ’s screen is much better. It’s brighter than the Axim’s and the brightness can be adjusted in more steps, so that at the lowest brightness level it is quite comfortable to have it in front of your eyes at the wind shield. The automatic brightness sensor is also handy. It works the same way as in HP4700 – you set the starting backlight brightness, and then it is automatically adjusted relatively to the set position depending on the ambient light.
Another important feature that wasn’t mentioned in the article is that the iPAQ has an anti-glare screen surface, whereas the Axim’s screen is shiny. As a result, the iPAQ behaves much better in sunlight. I wonder if it is a kind of integrated anti-glare screen protector and whether it’s a reason of the screen “feeling tough”. I ordered a BoxWave clear screen protector for the iPAQ, but I’ll think twice before applying it. The iPAQ’s anti-glare screen surface is brilliant, it doesn’t disrupt a brilliant VGA clarity of the screen a bit (unlike all the anti-glare screen protectors I’ve seen, effectively turning your VGA device into QVGA) and I don’t want disregard it by applying a shiny protector.
So, that’s the good side. Now bad:

• The iPAQ’s speaker is quiet. Very quiet. If you ever used Axim X51 as an in-car GPS, you know you could used it without any amplification – the speaker was loud enough. Now, with iPAQ you can forget about that. While driving, I wasn’t able to understand the iPAQ’s whisper at all. So, buy an amplified cradle or forget about voice instructions. On the other side, as for me, big and bright screen compensate for the loss of voice instructions.
• While using the iPAQ as a navigation device with a Bluetooth GPS, the USB charging doesn’t seems to keep up with discharge rate, even at “fast” charge settings. I noticed that after a couple of hours of driving with the PDA plugged into a cigarette lighter via USB all the time, the battery bar has actually decreased.