So I was wrong: W8 & WP8 to have a shared core.

Back in December I gave some fairly well reasonsed arguments about why I thought that the next version of Windows Phone 8 would not be based on the same underlying framework as the also forthcoming Windows 8.

Based on a leak reported yesterday (see here and here), it looks like I was wrong and I have 3 reactions.

I'm excited.
In many ways this is more than I could have hoped for. There are loads of cool features previously announced for Windows 8 that I would love to see and be able to use on the phone. And yes, also some I wouldn't.

I'm not counting my chickens yet.
There are still no public confirmation, details or timelines for any of this. I also wouldn't be surprised if we didn't see a greater similarity with Silverlight 5 than with WinRT in the short term.

I'm a bit nervous.
What will it mean for things going forward? (If advances in both platforms are to be kept in sync in the future.)
In the mobile space the market demands yearly updates. (Just consider the reaction when there was no iPhone 5 announced last year.--The 4S was considered by most as a disappointing stop gap to whatever comes next.)
On the desktop this (yearly frequency of updates) hasn't been seen in the past and is something that businesses don't want, as frequent (even yearly) updates become very expensive and awkward for them to manage. (Supporting the enterprise has always been one of Microsoft's strengths so I don't see them looking to upset the enterprise. Especially as one of the reasons for this initial synchronization and a lot of the upcoming changes are to support enterprise scenarios.)
Forcing updates to multiple systems to be permanently tied together just causes more work and slows releases. Microsoft know this and we've seen lots of products which were historically always released together change to be released separately and more frequently over recent years. I trust they're smart enough to do the right thing here (whatever that may be).