I work at a car stereo shop & me & everyone else that works there have all got cliffords..
i myself have a Concept 500 but with tilt & motion, remote start, remote headlights & all closure added.
Never really had many problems with mine except for user error when ive done somet wrong & the alarm has gone off becoz of it!
only down side of G5 Cliffords (i.e. the concept 650 & intelliguard 950 etc) is that their proximity sensors are not great.... nor are their tilt & motion sensors. (they are made by a diff company now in the far east!)
Also as there are new legislations with car alarm sirens the G5 alarms all use a "Soft Chirp" siren which basically means its much quieter than the G4s so the bark away warning is really pants! as is when you lock & unlock it!
best bet is to get a G4 if you can.... much better.