I just bought a new Sony Ericsson cell phone and my first impression is that the usability leaves a lot to be desired. And that's saying a lot considering my previous phone was 4 years old.
The problems are not learnability - everything is learnable. It just takes more steps to do everything. Accessing menus takes 1 or 2 more steps than the same things on my old Motorola. And getting out of a menu requires steps too. On my old phone, closing it did this automatically. And hanging up also requires a keypress when its on non-auto mode.
What a pain.
And there's more. There is no way to quickly put the phone on vibrate. You have to go four steps deep into the menu. Even putting it on silent requires opening the flip. This is often done under time pressure (one person's phone rings in the middle of a meeting and everyone else realizes they forgot). A basic tenet of HF is to create simple shortcuts for anything done under time pressure. Hello Sony? Anyone there?