Definitely worthwhile to use that benefit. The GOV matches up to 5% of your constributions with "free money" as well as the tax benefits you recieve by having the money come out of your pay pre-tax. There is also a great little loan program that you can utilize with the funds in your tsp account to make purchases at very low interest rates and end up "paying yourself" back the interest into your tsp account.
I always maxed out my tsp withdrawal from my check. It will pay off in the long run.
