I recently switched to a Rumor Touch from a more traditional slide-out feature phone. The touchscreen /sucks/, and it's worse since I've used smartphones with proper touchscreens and know what I'm missing.
Two things going wrong here:
1) Using a cheap resistive touchscreen instead of a proper capacitative. Even after calibration it's only got a rough idea of where my finger is, and the scrolling is jerky and slow.
2) Bad UI. Some of it (like looking at missed messages) requires precise finger placement to activate because of a stupid tiny icon. Also the UI in general is busy and poorly organized.
You might argue that this is what I get for getting the "free" phone with my contract and you'd have a point, but the fault is largely Sprint's because their store only had dummy display units (incl. non-functional screens) and I couldn't do a proper test of any of them except the iPhone, which was the only real phone in the whole display rack. If I'd known how fucking terrible this phone's screen was I'd never have bought it and stuck with a physical keyboard instead.