What is your desired asset allocation?
If you do this, you won't have the following:
International stocks (you'll have Ford, but not Toyota - saw that in another thread and I think it is a good way to put this in perspective)
Bonds
If you're OK with that, or have these areas covered in other accounts, then go right ahead. If you want exposure to International and Bonds, you could either stand pat with the Target Date fund, move to a life-strategy fund if you want an all-in-one that doesn't follow the curve, or move to a 3-fund portfolio and save a bit on fees.
Basically both choices you presented are defensible - you just have to decide what will work for you.
Regardless, you need to think about all of these things, and write down an investing policy statement, so in the future you can just execute the plan.