I have them in my Toyota Sienna. Fit and finish are great. I've also had Wet Okole seat covers and Coverking seat covers in other cars. In my opinion, the Clazzio were the best followed closely by Wet Okole. The Coverkings were pretty cheap.
The Clazzio seat covers are very easy to install (although they do take a bit of work/muscle to stretch the material over the seats). The only trouble I had were the headrests. Because of the material, it's a bit hard to stretch and I tore it slightly because I was bit too aggressive trying to force the covers over the headrest.
But anyways, to answer your question, I have the Clazzio seat covers, and in my opinion, they are a great AND cheaper alternative to professionally installed leather seats which would cost upwards of over $1000.
Of course, the Clazzio leather covers will never be as nice as professionally installed leather seats (or factory leather) but NO seat covers will be. The Clazzio's do come very close though. It took awhile for my family to even notice I had seat covers. They thought it was factory leather.