I went to the cinema and watched Insidious 3 yesterday, it's similar to the others.. Kinda getting old now.
Judging by the ending they'll be a 4th, which isn't that exciting.
i'd rate it 6/10, still think the first one's better.. it's scarier than the second one though.
Don't let the 15 rating put you off, it's still fairly jumpy for you horror fans.