Notices

For me, it's the contrary, my N900 has more readable screen on sunlight of all my devices, even with white on black themes (black on white themes are more readable on sunlight)

I'm very happy with how the N900 handles both extreme cold and warm. +35C last summer and -30C this winter, no problems. Well, one... trying to take a video of my gf down the slope killed the battery quite fast.. but then again -30C and a fast slope, the chill effect must have made it very cold Battery was green at start of the slope and at the end just enough power to shutdown.

I also have a screen protector and I haven't had trouble outside. At least I dont remember a time from last summer that I had a problem. Might be that time makes memories better but we shall see as the summer is coming soon.

I didn't like the anti-glare screen protector, it made the screen less transparent under regular light conditions.
The N900, aside from being ridiculously thick and heavy, is fine to handle outdoors (matte finish comes in handy), except when you start using MyPaint, draw for a few minutes, and then your palms get reallly sweaty beacuse as you can see in cpumem-applet, the phone's getting pushed really hard.
Uh, back to outdoors, it handles quite well in the 32 C heat in the morning, even if it's OC'd to 750. I never saw it push past 40C battery temperature.

If yours is affected by reflection, then it's not an anti-glare one.

If you have problems in sunlight you can try disabling the light sensor, that way the screen doesn't get darker in lighted places:

http://wiki.maemo.org/Disable_The_Ambient_Light_Sensor

i am very happy about my N900. I am originally from Berlin but moving to Kuopio(Finland) this year and i have been there for a lot of times already. Usually, i visit some friend near a place called "Kylmälahti" which is something about 30 km outside in the woods. My previous phone from another company could not establish a GPS lock there (with same operator and AGPS) and now, my N900 can establish a GPS lock in about 30 seconds without the need to be even connected to some internet connection. Dont have problem with the screen as well (as it can be very cold here as well) and in the night, the pictures and videos are just nice (compared to my Pentax digicam). Nothing bad to say expect the battery problems.. bought a solar power supply, 2 usb power cables, 2 other normal power cables and a car connector and i usually have at least 2 of them with me to be on the save side