I've seen two so far - By Jovi (who were OK) and Bongiovi who were very good. I spoke to their 'Dave' and 'Richie' equivilants afterwards and both where huge Jovi fans which was good.

Nothing is worse than a tribute band who only chose that group because the lead singer happened to look and/or sing like someone famous (I've seen a Queen tribute band who this applied to).

Basically - if a tribute band genuinely love the band who they tribute then they are usually worth seeing. I also prefer them when the frontman acts like themself instead of copying Jon word for word.