Are you working is Microsoft shop or mixed development skill set for different projects? Learn it would be useful where some projects required building from scratch and tight integration, I'm simply on Javascript where it cover almost everything + photoshoping.
If you plan to work oversea, Singapore, plenty of programmers use either Java or MS technology.
The majority of Fortune 500 companies run a mix of Java and .NET stacks, it is surely worth learning if you plan to work at a corporation that deals with these type of companies.
Do what you have to do to pay the bills and keep learning on the side. Either way you'll come out ahead.