The old firmware had issues with lagging on unresponsiveness but you can go to Nokia's website and download an application which will update your n800 solving the touchscreen problem.

Having said this, I know someone who works in Home Automation and he told me if devices like tablets with touchscreens have issues with buttons not being responsive this may be caused by screen damage. What happens is that some people use the stylus more than the finger tip which results in faster wear of the screen. So the people who are complaining that their screen has problems it could be because they use the stylus too much and put too much pressure on the gel type film which damages the cells of the screen. It's kind of similar to a computer keyboard fialiar, some people press the keys too hard and damage the thin film layer inside which contains all the data.

I've had the n800 for about 2 and a half weeks now and I have no problems. Another note: if you are a new comer to the n800 and what to dabble with installing apps on the device dont just delve right in because others are doing the same. If you do purchase the n800 in my opinion you should only install proper full released and tested softwares not beta 3rd party ones, this could potentially leave your device as a miere paper weight.

But I wouldnt let this issue put you off, the only issue I have with the n800 is not finding a free wifi hotspot in London, most of the ones I come across outside you have to be a monthly subscriber not like the ones on the train where you pay for by half hour, 1 hr slots.