First place while there are many things wrong with FrontPage it is not a bad editor. In fact FrontPage 2003 is a pretty good editor of its vintage but remember the web changes much more quickly than other areas. Since FrontPage was released there have been three new versions of Dreamweaver so of course it will have better support for standards and what is important to web designers now than a four- four and a half year old program. Besides most people who say "don't use FrontPage" have never used it or seen what it can do in the hands of anyone who knows how to use it properly instead of treating it as a web version of Word. People who do know how to use FrontPage don't use meta tags that say "generated in FrontPage" nor do they use the 1998 version which would "fix" HTML it considered broken. FrontPage grew up but the perception of it did not.
I can guarantee you that there are really bad sites created in Dreamweaver just as there are really bad sites created in FrontPage. Okay, there are more bad sites created in FrontPage but that's because FrontPage is easeir to use and costs a lot less so more people who are creating sites by going click, click, click are using it. I use both and have been using Dreamweaver since UltraDev 1 and even wrote the FrontPage 2003 to Dreamweaver 8 migration guilde so I do have at least a clue what I'm talking about.
Truth is you can create a really good site or a really bad site with any tool or method out there and that includes hand coding every character.
Now having gotten that little rant off my chest. :) Let's talk ablut Expression Web. You learn tehcnologies not tools. You can future proof only by understanding what you are doing and continuing to learn because the web evolves and changes all the time. What was state of the art and realy "hot" in 1999 looks like bad practice now becuase standards have changed. When is the last time you saw a new car sold w/o seat belts for example?
Expression Web is NOT FrontPage. It is easier to use than Dreamweaver.and right now has the best CSS tools - CSS is what you use to create the presentation layer or how the page displays in the browser. Expression Web creates standards complaint HTML that honors the doctype out of the box. This is what you need in any web editor since HTML and CSS are the basic foundations of web design and you cannot create a website without them.
Unlike FrontPage Expression Web is not tied to the development cycle of Microsoft Office and I expect it to be updated on a far more frequent basis, just like Dreamweaver.
RE ASP.NET - while Microsoft is the sponsor of ASP.NET and offers the best support for it ASP.NET is an approved standard that is open to anyone. You can get ASP.NET for Apache servers running on Linux. That version is created by the open source community and is available from http://www.mono-project.com/ASP.NET so it isn't just a Microsoft technology.
Expression is a web authoring tool, a good first generation tool. Is it perfect? Far from it but there is no such thing as a perfect tool.
Will it get better? Yes.
Can you learn Expression Web 1.0 and know everything you need to know to create great sites? Not really
Can you learn to use Dreamweaver and know everything you need to create great sites? Again the answer is no.
Don't think about this process as learning a tool becuase tools can't do it all and in fact a good web designer/developer never uses just one tool.
My view, Expresion Web is good. It is a valuable addition to any web designer's toolbox but it is not and should not be the only tool you need. Besides the price if you can get your hands on any version of FrontPage makes it a bargain. :)
Cheryl D Wise MS MVP Expression Instructor: starttoweb.com