As someone with some winforms and client applications experience - is it worth going back and learning the way traditional ASP .NET pages work, or is it okay with moving straight into ASP .NET MVC?
I'm kind of looking for pitfalls or traps in my knowledge of general C#, that I won't know from the screencast series and things on the ASP .NET site.
If you don't know how or haven't has experience with raw level web request / response and raw html/css rendering then MVC will would be good place to start. You will then better understand the pros and cons of both webforms and mvc. They will both be around in the future as the both address different needs.
Though I will say webforms is a highly misused and abused platform. So much of the "look no code" rubbish gives all who use it a bad name. Put in the time to understand it and use it properly you'll find its a very extensible and robust platform.
ASP.Net Webforms is a completely different abstraction over the base framework than ASP.NET MVC. With MVC you've got more control over what happens under the covers than with ASP.NET Webforms.
In my opinion learning different ways to do things will usually make you a better programmer but in this case there might be better things to learn.
I agree with Nick: MVC is much closer to the real web paradigm and by using it you'll be confronted with how your website really works. WebForms astracts most of these things away from you and, coming from a PHP background, I found it really anti-intuitive.
I suggest you directly jump to MVC and skip WebForms. As said, you'll be able to get back to it if needed.
It depends on your motivations. If you're going to sell yourself as an ASP.NET developer, you will need both.
If this is just for your own pleasure, then go to MVC.
My personal feeling is that webforms will be around for quite a few years more. So many people have time and energy invested in them. However, I think people will slowly (or maybe not so slowly!) migrate. Webforms was always just a way to get drag-and-drop VB4 morts to think about web development. It kindof worked but it does take away alot of control.
I can't really speak technically about MVC vs "traditional" as I have only used the traditional model so far. From what I have read though, I don't think one is vastly superior to the other. I think once you "get it", you can be very productive in both.
Practically though, I would take into consideration that most books, code samples and existing applications out there are written for the "traditional" way. You have more help available and your skills will be more useful for employers with existing applications written in the "traditional" way.
IMO, there are more pitfalls in normal web forms scenarios than with just MVC. Viewstate and databinding can be tricky at times.
But for MVC, it's just plain simple form post/render things old-school way. Not that it is bad, it is just different, and cleaner too.