I would like to just chime in again. As I this thread has made quite obvious, the framework, language, protocols that you enventually choose are very much debatable. When discussing "specifically" a Bitcoin business, which is what the OP has stated is his intention, I restate that security should be regarded as critical to your success. One bad hack and the results are disasterous as several Bitcoin business have already found out (the hard way). As much as I am enjoying the "friendly" banter, the point is sorely being missed here. Just go with what works for YOU.
As for licensing startups can get essentially licenses for up to three years using Microsoft bizspark program.
I was unaware of Redmond's Bizspark program, as I got out of ASP well before 2008. This is certainly a step in the right direction (a baby step at that), but nonetheless they are obviously trying to become more startup-friendly. I'd also like to mention that IE10 is again a great step in the right direction. FINALLY, I mean FINALLY deciding to conform to the industry standards (so I don't have to build a website for EVERYONE and then IE). If they make a version for Mac or Linux I think I'd actually be willing to install it and give it a test run.
Please correct me if I'm wrong, but I've found little to absolutely no ASP.net support when it comes to Bitcoin. Now, I will say that I haven't really been looking so I could have easily overlooked that fact. Back to the point, IMO the OP will probably find a smoother road to success going with a Bitcoin-friendly platform/framework/language like PHP and/or Python (I don't think C/C++ is part of this debate) based on an open-source hardware infrastructure. Things in the Bitcoin world ARE moving rapidly and I don't see it being easy relying on MSFT forums and support channels to get answers to your (Bitcoin security related) questions.
As ALL points are valid in their own right, considering the OP (and the Bitcoin-specific nature of this business), IMO the decision is quite clear:
(WARNING: troll-bait alert)- NO to Windows v.Anything go with Linux v.AnyDistro
- NO to IIS - go with Apache or Nginx
- NO to ASP.net - go with PHP or Node.js
- NO to SQL Server - go with MySQL (not my first choice) or PostgreSQL or FirebirdSQL (my personal favorite), even MongoDB seems to be quite interesting
You won't have to worry about licensing fees EVER-EVER and support will be plentifully abundant in the FREE forums.
For this I offer 2 bitcents,
S.