I think all of us hoping this would boost the market share of WP7 will be disappointed as well. I've visited various forums (both phone, and unrelated) and the general consensus is that it's just a mediocre phone.
Here is what I can tell you, from what I've seen, Nokia Lumia 900 is by far the best Windows Phone. It has great design, Nice camera, Nokia exclusive apps, Black Amoled screen, LTE capable and it's $99 or $49 or $0.1 or $0.00 after MIR, depending on how, where and when (your contract period) you are getting it. Combination of all these facts makes this the best Windows Phone that is out there in the market.
Now if you were waiting to move to WP from another device, you might want to think twice depending on the device you are currently using. If you are using an iPhone 4S, it's got one of the best screens and camera for any smart phone and has more storage options like 8/16/32/64 GB. If you are coming from a Galaxy Nexus or HTC similar devices, then they have the largest screens along with other HW related stuff like quad core or 1GB RAM, and removable storage card, etc. I will NOT compare the Apps because if you are counting the number of Apps, you should not even think about WP. But if you are looking at the ones you are currently using on a regular basis... most of them are already available and the other will be added soon.
With this in mind, I would suggest you make your decision. With electronics, the moment you get them, they are already outdated.
As far as the OS is concerned, you will always be able to upgrade to Apollo or Windows Phone 8 or whatever. But then I've not used a device beyond 6 months to an year. But that's me.
Every platform has it's own advantages and disadvantages. It really goes down to... WHAT WORKS FOR YOU.