I only had one - a Samsung Omnia and I liked it. I would prefer a slider mechanism and it is very important for me to get a German QWERTZ layout with easy accessible umlauts (Ä,ä, ö, Ö, ü, Ü ß). Sharp Zaurus SL-C 1000 had a good function to edit the keyboard functionality e.g. to add sticky keys and such things.