I saw Slash with Myles Kennedy at Glastonbury in 2010. I managed to be front row and get myself right in front of where Slash stands on stage (you can see me dancing on YouTube videos of the set). It was absolutely fantastic. Slash just keeps to himself. He knows he's a rock star. Myles Kennedy is an entertainer.
Faithless at Glastonbury were surprisingly good.
Like a PP, I've seen Bon Jovi about 7 times (lost count tbh). They've always been excellent, but the energy felt off on the last one, so I'm not sure about going again.
Def Lepard at the O2 were meh for me. Still have tickets to see them and Motley Crue in a couple of months, the weekend after I finally see Pink though! I've seen Motley Crue before, but Tommy Lee had an injured shoulder and couldn't drum, so hoping to actually see him drum this time. He did play some piano last time, but it's not the same.
I went with a friend to see Matchbox 20 about twenty years ago as her original companion was ill. She was a huge fan. I came away from the gig thinking 'meh, they were nothing special, but that support act was fantastic'. Said support act was a then-unknown Maroon 5.
Aerosmith were amazing at Wembley Area, not so good at Marley Park in Dublin. I think venue can make a huge difference.