Yes, I've bought via the device and wifi, but only when I'm in bed at night away from the PC. As there are a lot of authors I like i usually do an author search and then choose a book and buy . It's always been very simple and quick for me.
I've never bought from their suggestions though. and wish the Kobo Desktop wasn't cluttered with them.
Generally though I borrow from the library, try indie authors and download free books. A top author is a special treat.