I like those, because it's actually possible to get into the money with very conservative play most times. Since most of the ppl in these tournaments do a lot of all-ins with bad cards, you just wait for 1-2 good
hands and are likely to double up with these.
Buying the add-on is a) necessary and b) most times an advantage, because for some reason a lot of ppl dont buy it. They spent a lot of cash on multiple rebuys throughout the tournament while shooting for double- or triple-up early, but many miss the add-on, for some reason.
My personal ITM ratio is actually higher on Rebuy-Tournaments than on others, and I just buy the add-on, in 90% of those.