@ randersonnw, they are not for everyone, but you are here and you know better than 99% of consumers. So far I haven't seen any support in this thread for 401k loans, and I'm not surprised. Many people don't understand or trust them.
I've posted this list on the forum a couple times before, but it's worth posting again so people can understand what they're getting into. This is not all doom and gloom guys. These can be a very powerful tool, but just like a chainsaw, you have to know how to use it.
401k loan Pros:
Interest is around 4-5%, plus maybe $25-50/year fee, so they are cheap.
Interest is paid to yourself within the 401k, not paid to a bank, so you keep all the money.
It acts as a bond in your 401k (fixed interest, guaranteed return on investment).
You don't have to get approval from a bank.
401k loan Cons:
If you get fired/quit you have to either pay it back in full or withdraw the outstanding balance (So don't do this if you plan to get another job soon, or aren't in a stable job situation).
You can only take out the lesser of $50k or 50% of your 401k balance.
It takes away from your other 401k investments pool, so there's an opportunity cost since that money isn't invested.
You pay it back with post-tax money (you do this for all debt, but it feels different here as a paycheck W/H so worth mentioning).
You might not be able to contribute to the 401k while the loan is outstanding (I was able to when I took out a loan for an investment, all plans are different).
To answer your specific question, yes you have to make regular payments to repay the loan. However, if you are 6 months into repayment and you want to clear the loan, you can make a payment to do so.
I've taken a 401k loan for a very specific investment purpose, and it worked out great. I repaid it within 18 months. I have an extremely stable job and was not worried about that aspect at all. I have a partner who took one out during a house repair rather than wait on the insurance company to write him a check for the damages.
Market timing - this is no different than changing your stock/bond allocation. Life circumstances change, economic outlooks change, no need to skewer someone for changing the risk they are willing to take in the market. A 401K loan will just increase your "fixed income" exposure in your portfolio.