It's not a big deal on a small/personal scale, but it can become a bigger deal quickly on a larger scale. My employer is a large Microsoft shop, but won't/can't buy into Team System/TFS for a number of reasons. We currently use Subversion + Orcas + MBUnit + TestDriven.NET and it works well, but getting TD.NET was a huge hassle. The version sensitivity of MBUnit + TestDriven.NET is also a big hassle, and having one additional commercial thing (TD.NET) for legal to review and procurement to handle and manage, isn't trivial. My company, like a lot of companies, are fat and happy with a MSDN Subscription model, and it's just not used to handling one off procurements for hundreds of developers. In other words, the fully integrated MS offer, while definitely not always best-of-bread, is a significant value-add in my opinion.
I think we'll stay with our current step because it works and we've already gotten over the hump organizationally, but I sure do wish MS had a compelling offering in this space so we could consolidate and simplify our dev stack a bit.