The few people that acutally NEED a power conditioner are few and far between, and the need is due to the extremely poor power supply at their location, and as such, even the power conditioner may not be sufficient to really solve their problems.
Just remember, everybody needs a surge protector.
For most of us, the basic $35-$70 models are quite adaquate and will do all of the tasks required. I am partial to Belkin, the brand is readily available at many home improvement and office supply outlets, and the prices are lower than many of the 'net or audio speciality brands.