The target-date funds in 401(k) are good choises for first-time investors or for someone too busy to manage their retirement accounts.   They have a balanced approach to the retirement ages.  Instead of doing the asset allocation yourself, the target-date funds will do that for you. 

You just need to select your retirement year.  The funds will rebalance between equity and bond markets based on your retirement year.  For example: if you are in your 30s, the target-date fund will have 80% equity / 20% bond funds ratio, then, 40s 70/30, 50s 60/40, 60s 50/50 and so on and so forth.

Personally, I think that the target-date funds are not flexible enough for my investment strategies.  They really are funds over funds.  Rather let someone to choose the % allocation for me, I would like to do it myself.  But if you are comfortable with this approach, it could be the choise for most investors.  Actually, for the past 20 years, these funds have been added to a lot of companies' 401(k) plans.