[Windows Phone 7 General] The Gate Keeper:
Zune takes care of most of the common video files and converts them for you.

I'll clarify a few things for you from the posts above and focus it on your original post.

Zune itself is a little different to get use to compared to other media players, but it's quite lite in running, and grows on you over time. it's very well presented and works far better than iTunes that's for sure. It actually closes properly with huge libraries (try it on iTunes and watch the processes on your PC, see how long iTunes takes to close...).

MicroSD... it is definitely confusing, but from all the chatter, if you're after space, buy the Focus, use a Sandisk/Kingston class 4 32GB card, and you'll have a total of 40GB (8gb onboard). This trumpts the iPhone 4's 32GB offering. Which takes care of your space issues. And given you're in the US, get a Zune Pass and you get unlimited streaming of music (only limited to your carrier, don't want to blow your phone bill), and you get to keep 10 songs a month which is within the Zune Pass subscription.

Apps are growing, they're just about to pass 3,000. As a developer, i'm starting to get my head around windows phone. if you want to develop, it's far easier for windows phone than any other platform, and there is a lot of support online from MS and the community in terms of C# and silverlight (which is where you'll start). If you're not a dev, there are a lot of well known apps already available, and more coming by the day (e.g. wordpress is rumoured to be working on a wp7 app, which should be great for those who are constant bloggers).

Updates, yes carriers can block them, but only 1 round. Let me give you an example, say MS says that we have an update coming Jan, but at&t haven't finished testing with this update, they can ask MS to not deploy to their phones, and MS will not. Then MS comes along (let's say in may [made up]) and says, we have another update. the update that at&t asked not to deploy will be included with this, and at&t cannot ask for it to not be deployed. So you will at most be 1 update behind. This is awesome because not only does it ensure the carrier's can have their say, but in the end the end user will ultimately get the update, and not be left shafted like they do with Android. With Android, i'm sure you've experienced it already, but devices easily get left out in the cold when OEMs and Carriers are trying their best to push new products, and not worry about the older ones. And this is where you have to then start joining xda community and start rooting your phone to just keep it up to date, but then you don't really have a consistent experience and it requires you always checking back here, and in some cases flashing nightly.

As for whether it will be around for the long haul, MS has put HEAPS into this, a lot more than the kin (verizon is rumoured to bring the kin back anyways), and they've done the UI to most extent and now can focus on improving the current set of already high quality features, and bringing in new ones. This is all uniform across any windows phone. so when you go to pick up a different windows phone you can be assured you already know how to use it (yes... the iPhone style experience, but it does work and work well). And what would you prefer... a start screen that may look a bit bland at the start, but once you pin things you really want to it, it colours up... or have a sea of app icons to filter through to find that 1 thing you want... only to realise you hit the wrong icon when you get there (what I see a lot with my iPhone friends). Don't get me wrong though, I am a bit of a fan of different start screens that Android provides, but then you have to have all these widgets, and finding the right one can take forever, and if the widget isn't programmed right, it could be more problematic (causing instability, inconsistency in experience, and possibly even loss of battery).

In the end, each has their strengths and weaknesses, that's for sure. WP current weakness is the lack of apps, not all the common features in (custom ringtones as an example), and multi-tasking which everyone seems to have a big deal about now. Like i said on a different thread, when considering a windows phone, know what you do a lot of, find out if you can do it in windows phone, and if not, are you willing to give it up. Not to say that you won't be able to do it period, it could come in the form of an update, but look at it from the here and now, and then also would you be happy waiting till that rumoured update.