Review (5/5): Great fun with colors!
Manic Panic is the only non-permanent dye I am using now, after trying a few. It's vibrant, strong and lasts for quite a while. You need to be very careful, though, while you are applying it - it's very easy to stain bathroom surfaces (or clothes).
I don't bleach my hair prior to dying, as I want just strong highlights. I leave it on over the night, under plastic wrap and a warm hat. I love the dark purple shade! In the sun it looks fiery :)