One of the first things I needed to sort out on the P800 was a decent screen lock when in flip-removed mode. The default one is the bouncing Sony Ericsson logo which, being animated, isn't too battery-friendly. What's even worse is that when the screen is locked touching the screen will turn on the backlight. This means the light is likely to turn on when the phone is bouncing around in your pocket. A partial workaround is to use the virtual flip screen lock which does disable the touch screen, but I don't like the virtual flip and would never use it otherwise, so I don't see why I should use it just to lock the screen.
I set about looking for a replacement. My early searches resulted in an app called SClock. SClock will display a basic lock screen showing the date and time, and most importantly, it disables the touch-sensitive screen when locked. Problem solved! However as well as the lock screen looking distinctly amateur and generally unimpressive, there also seems to be a bug where the time digits do not appear the first time you activate the SClock lock. Nevertheless, I continued to use this for a few days, that is until I gave QuickContact a try! This is a replacement Contacts app which has an included Screen Lock module. This screen lock is just what I've been looking for! It shows the date and time, disables the touch screen, AND looks very slick! I've been using it exclusively for several days now and am very pleased with it.
Update (Jan 2005): getting a screen capture of the lock screen proved to be impossible, so here is a photograph instead: