This is definitely a hot topic right now for us with the release of Visual Studio 2012 (and .NET 4.5)... WHAT's NEW???
I will start by saying there is a TON of new stuff, but it can be boiled down to several large improvements.
I am not going to go into all the little things that have changed in the product. There are already some great resources out there that going into great detail on this, and I encourage you to take a look at those if you need this detail.
So, the IDE enhancements...what are the Biggies in my mind? First, there was a lot of work in the general IDE of 2012 to clean things up a bit. The general feel is the same, but seems like all the windows / layouts are more consistent than before. Coding syntax help (ie Intellisense ) is better, and more current ( HTML5, JavaScript editor etc ). Interop between VS2010 sp1 and VS2012 projects also now exists, so you can have devs on each platform on the same project. The obvious support of new frameworks ( MVC4, Entity Framework, ASP.NET 4.5 etc ). Search across the IDE... such a simple thing, yet its been missing. Nice new Code Review windows to allow you to work better with teammates. There are so many things to go into here, and this is where I would checkout the MSDN link above for deep details.
The .NET 4.5 enhancements focus primarily on scale and portability. Allows for the build of assemblies to work on multiple target platforms (phone,store,desktop apps). Many little performance things were addressed allowing for greater scalability. Obvious support of Windows 8 platforms, ASP.NET 4.5 enhancements with web forms, webapi etc
The changes to TFS 2012 to me are some of the best of the entire package. The best part of the changes though is that they aren't at the cost of change in direction... Its more about cleaning it up, making it more powerful, and adding new functionality. Way to much to go into here, but will refer you to the TFS Blog that has a good overview of the changes.
The packaging changes in VS2012 really revolve around the move of VS Test Pro down from Ultimate to Premium. There are definitely other small changes (including no more Premium or Ultimate w/o MSDN), but overall the message seems to be that Premium is the Bang for Buck SKU now. There are two good pages to checkout that break this down. First, is the full capabilities and feature comparisons between the products, and second shows the differences in the MSDN subscription between the various versions.
Lastly, we have been working hard at getting the word out... I know I alone have done countless Launch events for SLG customers across the country. If you have not been able to get to one of these, I encourage you to visit the virtual launch site with all the great content and demos on demand.