Although my personal development are very small projects, I can’t live without TestDriven.Net or Reflector. I haven’t used IoC, but I expect this is something I’m going to use from now on.
There is something to be said about developing in a big company. As opposed to to small group that can do whatever they want and keep the cost at a minimum, in bigger team there’s a bigger marginal cost of all the tools out there. If everyone uses his favorite tool, other people need to also know it to support it.
There should be some kind of a balance there for the optimal point.