1. Would I find all the apps I needed and used daily in the WP Marketplace?
2. Would I be able to live without multitasking?
3. Could Lumia's 8MP snapper take the place of the 12MP monster of the N8?
All these questions got answered and then some. So let's take it step by step.
Question 1: Would I find all the apps I needed and used daily in the WP Marketplace?
The Windows Phone Marketplace is full of surprises and hosts a lot more apps than Nokia Store does. You can find official apps for most services and social networks. Unlike Symbian, Windows Phone has an official app for Facebook, Twitter, Evernote, IMDb and so much more. I'm not saying the official apps are the best, but they're there and that means the platform is endorsed and will be supported for a long while. For an average user Windows Phone social networking integration is very well done, and basically removes the need for third party apps as far as social needs are concerned, but if you are a power user and want multiple accounts on Twitter and Facebook, then you need to find yourself a different app. What Windows Phone Marketplace misses compared to Nokia Store is the ton of HD games that made Symbian a gaming "phon-sole". Oh an the pay by SMS option too.
Question 2: Would I be able to live without multitasking?
Symbian is well known for it's brilliant multi-tasking and many think that the in transition to Windows Phone one may me missing that aspect. To be honest, at first you do miss the multi-tasking, but over time you get used to it and the resume app functionality along with the ability to have background agents working even when an app is dormant does make up for the lack of true multi-tasking. The resume-app approach was used my Microsoft to allow a smooth user experience even when multiple apps are started. The background agents work really well. Initially I thought that having no real multi-tasking would get in the way, but if the apps you use are well written, you have nothing to worry about. For example, I had an app that uploaded a large photo to Dropbox. The app had the ability to upload in the background so while I was playing Angry Birds the app took care of the upload neatly. If that's not multi-tasking I don't know what is. Windows Phone 7 is labeled as no-multi-tasking OS, but the matter of fact is that it does have multi-tasking, but not your traditional multi-tasking. Instead of keeping your entire app in memory doing whatever you need it to do, Microsoft used the background agent approach. The background agent is actually a piece of the app that uses no user interface and can do stuff in the background. For example, you may use an app that could eat 400MB of RAM when running in full UI mode, but only 20-30MB when running the user agent. That is called resource friendly app development.
Question 3:Could Lumia's 8MP snapper take the place of the 12MP monster of the N8?
Here is where I really missed my N8. The camera. I snap a lot of photos of my kid and lots of them are in low light conditions. The N8 clearly beats the Lumia 800 in this department, but when it comes to daylight I noticed that the Lumia 800 actually takes better photos, catches more detail. It's fast lens captures more light in broad daylight and it shows. You get less motion blur in your photos. So basically it's a trade-off. You get better photos in daylight and worse in low light. It's up to each and every user to choose. But I have to say that even in low light, the Lumia takes far better photos than other phones with LED flash. And that's, as I said above, because of the fast lens. The Lumia 800 does not claim to be a cameraphone, that's left for the 808, but it does hold it's ground against most smartphones out there.
Bottom line is this: it takes a while for you to get used to it, but once you do, you won't be able to move back to Symbian. The speed of the Lumia cannot be matched by any Symbian device. Windows Phone is missing some features, but it has others(lots of them) that more than make up for what you were missing in the first place.