Bogleheads is a great resource, but I expect most HN readers can handle managing their asset allocation manually (using a simple "three-fund portfolio" or similar), which allows you to save a bit on expenses compared to a target date fund, as well as take more advantage of tax management techniques like municipal bonds and tax loss harvesting.

This is very true. But for people who know nothing about investing and just want to get started, the simplest non-harmful advice I always give is "Vanguard Target Date Fund". That way, at least they are not doing anything wrong that will serious hurt their returns. Later on, when they have more experience or more money, they might want to switch to some other allocation.

Totally. I give similar advice (although we don't have anything quite as good as the Vanguard TD funds up here in Canada yet). Was just thinking for this particular audience it wouldn't hurt to suggest a bit more effort. Still, nothing wrong with a low-cost TD fund to get started, especially with a portfolio in the 4 or 5 figures.

In Vanguard's case, the TD funds generally make sense starting out given their lower minimum investment requirements ($1000 vs $3000 for most others). Once you reach $10-20k and can starting using Admiral funds, then you can switch to a three-fund portfolio and take advantage of lower ERs.

Have target date funds been successful? The last time I checked, their historical performance (admittedly for only 6-7 years) seemed underwhelming.

If you care about a 6-7 year window, especially the most recent 6-7 year window, target date funds aren't for you. They'll underperform when the market is doing well. They'll also suffer less when the market tanks. Overall, they're a safer investment if you really do have a fixed target date and want to retire close to that date, and thus you have much less tolerance for risk. In particular, they tune for less risk the closer you get to the target date, to limit unexpected surprises.

If you're near the beginning of your career, you don't have a fixed retirement date in mind, and you're investing a substantial enough fraction of your income that you will likely retire earlier than average, then you might want to pick a standard index fund with a fixed proportion of stocks and bonds based on your tolerance for risk, and leave it that way.

The last 6 or 7 years hasn't exactly been average for historical performance in either stocks or bonds. I'd expect that the target date funds would wind up underperforming in this sort of market, and likely outperform in down markets, especially once you factor in ill-advised market timing/panic changes when the bottom drops out.