Hi Rob
I have a Chemspec pile lifter vacuum which i use mainly for commercial heavily soiled matted down carpets. And believe me it beats your average upright hands down for power and performance.
On most domestic cleans a sebo will be more than adequate for the job, and a heck of a lot lighter. I have used the pile lifter on domestic carpets mainly if there are loads of dog hairs but very rarely. When i have used it the customer response has been very positive as they perceive it to be something more than just normal vacuuming, especially as it brings up the pile.
On the whole if you are just doing domestics you wont really need it, and you need to justify the high price tag and extra weight in the van.