I have come across many theme providers, but I rate mythemeshop as the most beautiful theme providers for wordpress. Other than that I would like to say that I have learnt a lot about premium themes after buying one & testing it ....however I don't use it for productive website, but definitely I learned a lot...Lastly, I use a free theme called "Point" & it has paid me with great design & is attracting more users. The support team is also good ...i hope they continue working in this manner....thanks