The Ultimate Stopwatch & Timer for Android has just made it passed the 'final milestone' of 250,000 installs, great stuff. It's my second app to have reached the dizzy heights so far, the next is a couple of months away yet at around 150k. Seems like new device sales are keeping the install rates strong. Reaching 250k has a bizarre effect of dramatically increasing install rates. It is apparently a far more complelling proposition to install an app with >250k installs, almost as if the user starts believing they're missing out on something great. Battery Widget has rocketed from 250k to 450k installs in less than 2 months.
It seems, even though the Android Market is getting pretty busy these days, that if you focus on users desires it is still possible to get decent traction. Live Wallpapers are the sweet spot at the moment, they are being searched for by Nexus 1 users and a decent one will get thousands of downloads in the first week. I spent an hour creating 'Duck Paper' last week and it is now at 3,500 downloads. Content apps are a little trickier, especially if you don't have a recognised brand behind you, make them specific and easy to use, then update weekly.