The following is my list of settings that I use on my N810. I use KDE pretty much exclusively. I only go into Maemo anymore if I need to do a one click install of an app/update (ie: no deb available).

1) First I'll start with how to get around the fact that some of the windows are too big for the N810 screen. What I've done to make the windows that are too big accessible, is to go into Control Center -> Regional & Accessibility -> Keyboard shortcuts -> here you can assign buttons to do various tasks while in KDE. For example on my N810 there is a "menu" button to bring down the menu in Maemo apps - that is pretty much worthless as is in KDE (KDE just recognizes it as F4) so I assigned it to "Move Window". Now whenever I want to easily see the bottom of window that are too long (mainly so I can tap OK/Apply/Cancel etc...) I just press that button and then use the stylus to move the window to wherever I want it.

2) any N810 owners should use Control Center -> Regional & Accessibility -> Accessibility -> Modifier Keys -> Check "Use Sticky Keys" and "Lock Sticky Keys". This will allow your Fn & Shift keys to work like they do in Maemo (ie: Tap Fn then tap the 2nd button instead of needing to tap both at the same time).

3) I've also mapped the "Home" button to "Minimize" and "Shift + F4 (menu button)" to "Close" and so on until all of my buttons were mapped to what I want. You can also do alternative assignments for each of the commands which is handy if you're using a BT keyboard so using the keyboard uses buttons/keys that are convenient to it and my BT keyboard has it's own set of shortcuts.
You can also make application specific keyboard shortcuts - for example when I'm in KOrganizer, Ctrl +N will bring up the New Event dialog. You get the idea...

4)You can add/remove applets from the system tray and panel. If you tap on the left side of section of the panel that holds the item you want to edit, you will see a little white criss-cross verticle line with a tiny arrow at the top. Tap on that arrow and menu will pop up that allows you to edit the panel. It can be tricky to tap the arrow, so be patient if it takes a few tries.

5)Because I use KDE all the time, I wanted as much memory and CPU available for it as I could get. So I turned off all applets, email etc in Maemo.

That's at least a start...I've gotta run but will add more later