Microsoft has started advising MSN users that they need to switch to Skype, and that the MSN servers will be shut down on March 15th, 2012. [CNET article]
This isn't entirely surprising, it was always a likely move once MS bought Skype, but I think it's good that they're setting a hard and aggressive cutoff date, and also communicating it early. MS has a bad history of either letting services/products linger far too long, or dropping them without any notice. We'll see if there's much end-user backlash -- so far I haven't heard of any.
I don't particularly like MSN, but use it a lot for work. I've been using a 3rd-party app (Adium on the Mac) that supports OTR so my messages are encrypted in transit, but the encryption sometimes goes out of sync requiring manual steps to re-initiate the encrypted conversation which is a pain.
From what I understand, the Skype protocol (at least for voice and instant messages) is encrypted by default, and it's also a peer-to-peer model so messages shouldn't be going through a central server at Skype/MS for snooping.
On the other hand, Skype software is closed-source, so who really knows what data they may be gathering, and there are no 3rd-party apps available which rather sucks.
I found the transition from MSN to Skype pretty simple -- I got the Skype 6 client, and when it prompted me for login one option was to use a MSN account. The first time you do this, Skype will transition all your MSN contacts (but not categories/groups of contacts, it seems) over, and there's also an option to merge your MSN login with an existing Skype login. From that point on, you login to Skype using your MSN login (since it doesn't support multiple accounts), and you can use the Skype client to talk to anyone still using a Messenger client or using Skype.
One thing I noticed is that the Mac Skype client doesn't have support for modifying contact lists (similar to groups in MSN) for organizing contacts, but I was able to set them up and assign users to them in the Windows Skype client and the changes I made there showed up in the Mac client. Haven't tried the Linux client yet, don't have a running Linux with GUI that I can easily test on at the moment, but I expect it will have it's own set of issues.
Generally the transition seems to be fairly smooth, though the Skype client is pretty clunky. It'll be interesting to see what happens as we get closer to March 15th, and then on the actual day they shut off the servers.