Is it a better deal than normal life insurance?

It will depend on your health condition, but I think you'd likely get a better term deal with a different provider. If you buy a 20 year term policy, the rate is locked for 20 years. VGLI premiums increase as you age.

Also, your VGLI coverage amount cannot exceed your SGLI coverage amount in force at the time of separation from service.

VGLI rates are here: http://benefits.va.gov/INSURANCE/vgli_rates_new.asp

if you are in good health, VGLI is a bad deal as you get older. You can get equil ins outside for half the cost over 45 yrs old, if you qual for the preferred rate.