I have one. Don't know how good it worked because I got a bad set of gauges.
It will really wear your compressor out. Instructions said to pull a vacuum with the pump for 30 minutes. Seemed to me if it takes 30 minutes it really doesn't have much draw.
On the bright side I did complete the A/C repair I was doing and all was fine.
Someone will get a good deal on a lightly used pump at the next garage sale.