Not big.

I'm not talking about the slide to unlock screen. I'm talking about the number code unlock screen.

@JonWW
Interesting, but I'm not entirely sure it's the sole cause. There are definitely situations where what you say seems to happen - for example, I use QTspot a lot and sometimes, when that's running in the background the lock screen takes about 20 seconds to be responsive. It's not a dev issue as much as a memory issue I know - as it also happens with other non-dev programs when I have a lot of memory-hungry programs running. The real problem is the speed of the operation even when nothing else of consequence is running, and it's mainly a physical problem.

On any other phone it's literally two seconds when I fish the phone out, activate the screen and type in the code one-handed. With the N900, what I have to do to get it to unlock first time, every time is to fish it out, turn it landscape, hold it in both hands and carefully locate my nails on each key. There is definitely an ergonomic problem to do this quickly. With the iPhone for example the activation button is on the fascia, while the capacitive screen accepts 'pad of finger' inputs just fine - so unlocking is a seamless action. With the N900, I have to precariously balance the phone while gaining access to the activation slider with my thumb, then change my hold to be able to prod the numbers with my nails because pad of finger input almost always fails to register properly when you're prodding in a hurry.

I'm thinking that if the lock screen was turned portrait with the number keys lower down the screen, they would be easier to press while holding it like a phone.

Most often, I e.g. have to make another call after taking one - and it is immensely frustrating when you're in a hurry to unlock the N900. Part of it is down to the response of the buttons - and I'm not convinced that's solely a memory issue. And part of it is the location of the buttons when being held portrait.