It's not such horrid advice to follow.
As mentioned in another comment already, Loopt uses ASP.Net in addition to other Microsoft and open source technologies.
If I could start over, I'd use it again.
ASP.Net the framework is great. By framework I mean the request pipeline and everything else on which the high level items like the TextControl are built atop. There's a lot of crap at the top (built in controls, page viewstate, etc), but you're not forced to use it. Hooks are exposed at almost every level of the stack where you can override the default behavior to do what you want (and I do). The trick is knowing when to NOT use the built in stuff.
Also of note is that while ASP.Net necessitates IIS and Windows, it doesn't lock you down any further if you're willing to take a few risks (no vendor support). From the beginning Loopt's website has used a custom session state provider: At first it stored all user state in encrypted cookies, but now it's moving to a fault tolerant, distributed Erlang based store. Results from PostgreSQL servers running on FreeBSD power many of our GIS based features. *nix based boxes perform all of Loopt's geocoding and map generation tasks.
At Loopt we try to pick the best tool for the job. Sometimes it's sold by Microsoft.
Sidenote: You can pay for Microsoft software on a per box per month basis, and only pay for what you use. I think that Windows Server Web Edition is only about $10/box/month. Not actually that big a deal in the big scheme of things. For example, good developers are WAY more expensive than software =P