I am, as an advertiser. The advantages are mostly the prise and the low number of competitors there. Not so attractive to me at this time, but there is a lot of potential in there.
All you need to know is to mange it right and the most important - know that your audience there are byers. One thing I do not like about mobile ads. Users open the mobile app or browser, check what they need and close it. To fast for any advertiser to grab the attention of their potential users.
But, as I said, you can still advertise there, in apps, in mobile sites.