I've been using it for about 3 weeks now. There are quite a few bugs. There are times when i'll turn on Sling TV and it will take a good 5 mins just to start streaming. Sometimes it won't allow me to change the channel. And It does buffer a lot. I've had times where I would be in the 3rd quarter of a basketball game then all of a sudden the game would just start over.
With all that said, I'm gonna keep it. I really don't watch much TV, and I like how the basic package carries all the stations I do watch (espn, tnt, tbs, amc, hgtv). Plus, it saves about $40/month off my cable bill.