I've got one installed in my PS2 at the mo' and it really is the business! Everything that I could want from a chip, macrovision removed (RGB me up landlord!), all region DVD, DVD backups (both films and games), backup CD games, PS1 games, stealth mode (for online gaming etc), divx and other features. You can't go wrong!
All this and the chip uses the same voltage(?) level as the PS2 so overheating is not a problem!
The only slightly annoying thing is having to hold down a certain button on the controller to access the different modes i.e. DVD video hold down square from when you turn on the PS2 until it boots the disc, circle for PS1 games or triangle for DMSexplorer. All PS2 games boot automatically without doing a thing.
A very good chip that I warmly recommend.