I switched from Symbian to WP8 and after some initial teething troubles, I've really grown to love the OS.
I've had to accept to loss of a few features which were standard on phones such as the 808 and N8 as well as the ability to open up the OS as I did on Symbian to create custom roms but once I got over that, it has been a great experience. Besides, in time the OS will become rootable which brings a lot more freedom but also some risks.
I'm not a user of social media so the lack of a few popular apps in that category hasn't bothered me in the slightest but I would really like to see a dedicated banking app from my bank. Apparently one is in the pipeline so it's just a matter of time. Also, a BT Sports app with streaming ability would be great as would a Sky one plus it would be cool if the BBC invested a little effort into creating some WP8 apps. There are a few third party ones which are good but it would be nice if they created some themselves.
The OS itself is very smooth. I'm having trouble believing that someone on here insists WP8 is horribly laggy as I haven't experienced anything like that on any of the WP8 handsets I have used. Some of the live tile apps are very good as are the many lenses apps that enhance the camera experience. Most games I have tried have been pretty good too. That isn't to say that all apps I have tried have been great as quite a few have been utter gash but this problem exists on all platforms. As well as using Symbian beforehand, we also have Android and iOS devices in the house and crap, useless and sometimes potentially dangerous apps exist on those marketplaces too.
I have been so impressed with WP8 that I have given the missus my old 920 and upgraded to the 1020. She is very happy with the 920 and we're even getting a WP8 phone for our daughter for Christmas.
As for the 1020...I have been utterly blown away with some of the images it has captured. Yes there is a post processing delay which takes some getting used to, especially if you have the camera set to capture in 5MP and full resolution modes but the end result is very impressive. The full resolution images have been great for resizing and improving the original shots. In fact, having the full resolution copies on hand have made an amazing difference on a few occasions. On one such time, I was photographing fireworks with a long exposure setting but without realising, I had zoomed in a bit for a few shots. When I realised, I corrected the zoom and carried on. Later when reviewing the images, I was a little disappointed that some of the subject was out of frame but I was able to save the situation by resizing from the full frame full resolution image. Managed to convert quite a few disappointing shots into impressive images.
The pinch to zoom detail on the full frame images is jaw-droppingly good too. However, if I'm perfectly honest, I do think the images captured on my 808 were a little sharper but this is something that Nokia are working on with their Black update. Add to that RAW support which is bloody amazing for a smartphone and things are looking very good indeed.
I was very sceptical about making the switch at first. I loved Symbian and clung on to the hope that it has a future when it was pretty much dead and buried. My experiences with Android and iOS failed to convince me to switch to those platforms so I took a gamble with WP8 and I'm glad I did.