I am looking for a simple GTD / taskmanager app. All the things I tried so far (both mac and PC) tend to get clumsy and bloated with features.

I am just looking for something way more simple, as an offline (desktop) sproutliner. I currently use Smultron (a OS X notepad like app).

Any suggestions?

i just discovered that i can display and edit a sproutliner outline from my desktop -- several separate ones, in fact. i used the "active desktop" function of windows xp (i hear it's unavailable in vista, tho). start by entering the desktop properties, click "customize desktop" from the "desktop" tab. click the "web" tab of the resulting "desktop items" dialog. add a new web page, and provide the url of your sproutline. it will synchronize when you're online, and just hang out when you're not.
i wouldn't know if there's a way on mac ...