I am currently working on ASP.NET MVC 1.0 framework. My team is involved in developing a web UI for a localized application. Our team was lucky to have the choice of choosing the technology stack that would suite our requirements. We decided to use ASP.NET MVC so that we can use TDD to test drive the project work. Earlier I had worked on web application with ASP.NET 2.0 with MVP implementation. I felt it wasn't very TDD friendly. Since ASP.NET MVC 1.0 offered very good support for TDD we decided to try it out.
With whatever little I have worked with MVC 1.0 I felt that on its own it had few limitations like client side validation, support for some of the common functionality like Grid controls which a ASP.NET developer is well worse with. But many of these limitations are addressed by the MVCContrib community project. I am still working on getting to know the finer nuances of MVC 1.0 framework but the next version MVC 2.0 is released for preview 2. From whatever I have read it seems to be improving all the time and I feel it will still take a while to be stable and more usable. But it is headed in the right direction and the community is adding a great value to the things which might be missing right now.
Another advantage I see with MVC framework is it is bundled by default with JQuery. Since JQuery is widely accepted standard life becomes easier. From Phil Haack's blog I read that some of these limitations have been taken care in the Preview 2 of ASP.NET MVC 2. I look forward to try those things.
Here are few articles which highlight the features of ASP.NET MVC