>I would discard .NET - I see no reason to switch from one Windows-only system to another Windows-only system.

Learning "MS" .NET is not a waste of time; you can transfer what you learn (including C#, ADO.NET, ASP.NET) to the open source implementation of .NET.

http://www.go-mono.com/

Of particular note was an installation in Munich, Germany, supporting 350 servers and 150,000 users.