I believe there is an option to have the screen always on while charging. Check in your options. I do believe it is there.
Edit: Ehh, i just looked and cant find it. Although When I leave mine on charging, it stays on. And I can push lock button to turn the screen off and back on. Ill have to check if it constantly stays on though.
Sorry to bump an old thread, but the Stay Awake option is missing from the 2.2 update. I found this very useful for keeping the screen awake while plugged in and driving. I could just glance at the traffic on googlemaps, or tap the skip button in music player, or have ANY app stay awake so I could just glance at it without having to find the power button and swipe the lockscreen away which takes my eyes off the road. So now I'm back to that mess, or using car mode, which has limited apps fixed to it.
Is the setting in a different place or just gone, and if its gone, is there a workaround? Is this in all 2.2 updates, or just on captivate? Is it the same for 2.2.1? Really annoying that they removed a feature I used everyday!
I use an app called "StayAwake" by runks. Freebie and does exactly what you need. I drive all day and need my captivate to stay on.. don't really care if the screen burns or not.. they make more phones all the time!