Will the CSS styles, classes, etc pretty much be the same in 2.0? I've made many changes to the styles in 1.9, and if they are significantly different, then that means I will have to spend a great deal of time tweaking the styles again which is a very tedious and time consuming process. Also, will the ASCX controls still be there, or has this changed? I'm going to download the source this weekend to check it out, and I will be Beta testing as well.
Given it's a move to MVC I would venture to say the ASCX controls are probably gone, in favor of partial views, but that's just my guess.
For those out there that are just starting to use Nop Commerce (like me) what I would suggest is you keep it in source control and create a branch from the main code stream with all your changes. That way you can merge those changes when a new release comes out.
Granted, my guess is the MVC release will have massive changes in terms of the presentation layer...
I'm not involved in the development but I've started working with the 2.0 version some time ago, so this answer is based on my observations so far. The css is almost identical. However, the 1.9 user controls won't be usable since version 2.0 is mvc based. So there will be some work to be done if you changed the layout other than by modifying the css. But the site structure is quite the same.
It is nice to know that you are working on Nopcommerce-NHibernate. What is the expected date by which you will finish this work. I hope that we will find this code on codeplex.
I am curious to know what files/projects would be modified as a result of this.