If you use a modern high end PC its smooth, on almost everything. By smooth we mean its response is done in the low 10's of milliseconds, maybe 100ms maximum. A lot of the entry level hardware is quite sluggish, especially hard drives, but you can get an incredibly smooth responsive system today in the higher end hardware because there is plenty of power available to run at very high speeds with very powerful CPU and GPU combinations at high resolutions.
A mobile phone on the other hand is incredibly limited in performance. CPU performance in total is no where near even a single core of a modern CPU and the GPU is equally very limited. This causes a lot of obvious latency and performance problems. In no particular order:
- Scrolling web pages is pretty slow, when they are partially rendered scrolling up and down sometimes becomes impossible, the device just stops responding.
- Opening a website while one is loading in the background often has the users press ignored for several seconds.
- There is a noticeable latency to the home screen as you swipe it left and right that means it doesn't feel attached to the movement you are doing.
- Many games have noticeable input latency which makes the characters harder to control or make it harder to aim.
- Due to the way mobile data is done performance is often extremely poor going out to the internet but the phone seems to literally work hard just downloading the latest twitter streams or updating news sites in the background which impacts whatever foreground app it is you are using.
The basics of email, web and video are all impacted heavily by performance problems on modern devices, its not just a lack of smoothness its whole seconds of unresponsiveness and jittery playback. They barely work at all. If that happened on PCs on a daily basis these forums would be flooded with people asking how to fix it.
I could go on and on and on about all the performance problems I see on my mobile and on my tablet, because they are obviously there pretty much everywhere. Mobile's are still incredibly low performance devices and they show they struggle ever day. Many people don't care, performance is good enough to get the job done, but I also think these glitches and moments of poor performance and general lack of smoothness are something that frustrates people. It certain frustrates me. Doesn't mean the device is useless, but it means I am a slave to it not it being a slave to me. The device should be waiting for my input and it should feel instantaneous in response, I should not be waiting for my device to catch up with what it is I am doing. I don't like waiting for computers, its dull and productivity sapping.
So I think smoothness is a big deal, I am fed up of watching my phone and tablet choke on something that should be simple, but is unfortunately so resource constrained that its barely keeping up at all.