I think it’s well worth going to see them, a very fun day out.
Apart from Gary Mullen the rest of the band are just a cover band, not a tribute band, the guitarist seems to try and stray away from Brian May's sound, even filling in some of his own riffs. One Night of Queen doesn't have the greatest "Queen sounding" band, there are a few other tributes with much more accurate bands, but Gary's almost spot on 1980's Freddie sounding vocals are pretty unique and make up for it.
You can see what others have thought about them by using the search button,
There's been 4 or 5 threads here praising them over the last few years meaning a lot of other people are happy with the show.
Of course this is only my opinion, yours might be totally different, just remember no bands will ever be prefect, but queen themselves.
One Night of Queen are brilliant!
I went to see them last year and enjoyed it so much that I'm going again this year.
They're really good and Gary Mullen's vocals are amazing!
Queen of the Bohemians
I saw them last year. I didn't really know what to expect, since it was the only tribute show I've ever been to. It was fun, and Gary got the crowd to come up to the stage, so there wasn't the awkwardness of everybody being seated. I'd see them again.