I have had one for 20+ years. Rock solid. Has saved me lots of money stringing. I know exactly how each string job was done, which is great since I have OCD. Only downside is that it can take a while to string racquets while watching movies - I spend about 1-1.5 hours on each string job. I only string my own racquets.
I have come to the conclusion that I simply don't know what I don't know.