[Andy]

To be honest it is a little more difficult to learn from scratch as its not based on the same sort of system as PHP. For instance you would only code in PHP and learn and use functions like connecting to a database (MySQL or others)
With ASP.NET you have to learn either Visual Basics or C#, in my case i was a C++ programmer anyway so switching to ASP.NET wasn't a serious issue as i had learned the basic language before (when i say basic i mean the syntax for C# and dont recommend a developer to start with C#, start with VB first)
once you can code in C# you have many function built in but most can be written from the C# syntax rather than the ASP.NET frame work.

Costly because there isn't any real helpful sites or books to get you started from a complete novice.
For starters the hosting is more for ASP.NET account other than linux systems. or in my case building and buying a complete server solutions in MS including the MSSQL.
Although the company i work for pay for this setup and have more commercial feel its still expensive to learn from my end as i had to pay for a vmware fusion license so i can run the campus agreement xp pro on my mac. i am disappointed that Microsoft have not spent time to creating a gui for mac as of yet!
I prefer ASP.NET because of the commercial feel to the scripts and how other people may see the scripts i have created looking very professional.

Dont get me wrong being a mac fan i love open source and dislike Microsoft as a hole but PHP was the first web developing language i learned.