I know exactly what you mean.  Frameworks like Monorail have spoiled me to no end.  But before I discovered the goodness that *is* MVC web frameworks, I was fairly successful for a couple years implementing web forms projects using MVP.  It's still far less than ideal, but if you can get as much "stuff" out of the code-behinds as possible, and into your presenters, it can make your life a bit easier.  So if you decide you can't make the switch, perhaps consider refactoring towards MVP, if possible.

I'm getting ready to feel the pains of webforms again soon myself.  I'm temporarily getting thrown on an existing web forms project with a large code base and 0, count 'em 0, automated tests.  

After using Monorail pretty much exclusively for the past year on various projects, the decrease in productivity when moving to web forms is going to kill me!  :S

I'd be very careful in that line of thinking, because it is a typical programmer mentality and usually doesn't equate to business value (or $$$).

But that doesn't mean you're wrong.

I'd say, make some minor adjustments to the code that get you half of the way there.  Take small steps.  Just like you wouldn't take a 2 month break to back fill a bunch of unit tests for an application, you can't take the big bang approach here either.

Right now if I was doing a new project I'd pick Monorail.  I would still probably port that to ASP.NET MVC once it comes out, but I think that it would be pretty easy to convert.

All I would ask is this: From a maintenance perspective what would be quicker/easier in the long run?  Personally, I think the maintenance phase is the most important phase of a project and that it often does not get the consideration it is due. If you have to spend the $$$ up front to port, how much will you save on the backend? As someone who has had to deal with large web forms apps, I bet it could be a considerable amount.

@Joey - I am using MVP in the existing code...The problem is that the app requires very intensive ajaxey forms AND I have grown a ton since this app started so I kind of have an over-architected headache.

@Ben - great counsel and I agree. However a red flag to me right now is that I am not as flexible as I'd like to be in responding to model insight.

@JP - I have to agree here with you, esp since I AM the programmer/dba/infrastructure team.

I wouldn't wait on MS, do what you need to do today to solve your problems.

If it's true that viewengines would be supported, there is a good chance your migration would be minimal?