I'm sorry, but I have to disagree with you there (the "all in" comment). I'm kind of in the same boat. I learned BASIC and vb first, then some PHP, but I've been doing MS-related work for the last 12 or so years. The MS ecosystem is definitely segregated but that doesn't mean you're stuck only doing MS work forever. Over the time I've been programming, including doing MS work, I've been learning so many other technologies and it has also positively impacted my work on the MS side. New ideas for how to lay out code, new technologies to integrate with, etc.

You may not have made the right choice, but it's not because you chose ASP.Net over PHP (you'd probably be asking the same question if you picked PHP). It's because (and I'm sorry if I'm being too blunt) you didn't seem to question what you were doing or go out and seek alternatives. You mention the "drag and drop" world, but that's not the only way to implement those features. We both worked in the same world at the same time, but I didn't like the "magic" the drag and drop functionality provided. It didn't give me enough control over what I wanted to do so I figured out how to do it manually.

My response is a bit more rambling than I intended for it to be and I hope you can piece it together. :) My main point is that we both ended up with the same choice (ASP and ASP.Net) around the same time but I also have those bullet points you mention checked off. I don't regret my decision one bit and I don't think it has stunted my professional growth at all. If anything it has probably helped it because .Net devs are in high demand and highly paid in my area.

Edit: Hah, I wrote this post without knowing who you are at all. I may very well be wrong, but that was the impression I got from your comment and the original article.