I got my 5800 about a month ago, from Virgin, which uses T-Mobile as a carrier. I have to say I was pretty happy with it, and I believe it shipped with version 40 firmware. The issues you describe were not and are not (have upped to version 50 - changed product code to do this) an issue on my phone, its pretty responsive and the screen rotate is fine - i have noticed for the screen rotate to be quick responsive the phone needs to be held vertically, ie perpendicular to the floor, whether landscape or portrait, then the screen rotates quickly.
The issue i have had from the start, and had REALLY hoped version 50 firmware would have sorted out, was the 'swipe to answer' feature on incoming calls, and also on the alarm off/snooze. it just doesn't work. if i unlock and relock the phone then it does work, but this defeats the object of having the swipe option surely!! Anyone else got this issue?
When i upgraded, after changing the product code to British Isles generic, then i get firmware version 50.0.005.c01.01
i have read online that there are c02 and c03 versions, i wonder if this is location, and even changing product code does not get me any other firmware, neither OTA nor NSU. that's another question - is it possible to revert to firmware v40? if i could do that then i might try and upgrade again using a EURO product code to see if i get the c03 version, as apparently you get quick office with that for free. though im not sure if this is the case...
oh well, I'm hoping issues can be solved as i really DO like the 5800, and hate it when little niggles ruin the fun of it 😃
P.