Well, if you want to write an OS, a critical real-time system, or a high-performance scientific data analysis suite, then no, .NET is probably not for you (although .NET 4.0 and its parallel processing additions certainly improve matters there). But if you want to rapidly develop enterprise business applications (or indeed webapps - everyone here appears to have overlooked the massively popular ASP.NET), then .NET's pretty damn good.
The strength isn't really in the idea of the CLR or whatever - that's an implementation detail. It's the huge framework of ready-made classes that accelerate development. Sure, there are plenty of PHP frameworks and so on, but with .NET, and C# in particular, you've got a massive library ready, tightly integration tested, and virtually guaranteed to run on anything from Windows XP up... oh, and I've rarely found a .NET app compiled for Windows which wouldn't run without modification under Mono.
As I suggested in the subject line, it's a matter of tools for the job. I regularly do C#, Obj-C, C, JavaScript, Perl and the odd bit of PHP and Java, and C#'s my favourite for headache-free development. It's not perfect for *every* job, but for the ones where it works, it works very well indeed.