It's safe but the flavor will depend on how it was packaged. Freezer burn only happens due to cold air around the meat that has very low humidity to take the moisture out of the meat. If it was vacuum packed, it wouldn't taste much different than fresh bacon.
There's this local meat shop around my place that sells meat packaged 6 years ago that's sold to chain restaurants. They're vacuum packed and stored in the freezer. They certainly don't taste peculiar.
No, they just have the same nutritional quality as the the plastic they're sealed in. The government spends huge amounts of money researching methods for preserving food longer and they have nothing that lasts anywhere close to six years.
To paraphrase Emeril Lagasse, you could spread it on a bumper and make it taste good but, why would you want to eat a bumper?
I also think it more likely the meat shop sells to institutions (read schools) than chain restaurants but never underestimate the greed of corporate food service.
To the OP, it won't kill you but, in the spirit of experimentation, go get a fresh package of bacon and taste them side by side.