I like them and go by the maxim that as long as you feel you are playing well you should always rebuy/re-entry/addon.

I don't think they're good for the game. As Negreanu said (he likes them, but also doesn't think they're good for poker), re-entry tournaments favor professionals with deep pockets, who can rebuy multiple times, which means the field has a higher concentration of professionals. 

They favor good professionals who don't mind playing against other regs, while the rest of the field (break even, slightly winning and losing players) is at a disadvantage.

Its def bad for the game, recreational players will have even less chance to make it deep into the tourny because the pro's can just re-enter and re-enter as much as they like. Even on Day2 of some live tournaments. Its great for the casino as they get more rake but just bad for the game overall as recreational players might decide not to play them.