I switched from an Apple TV gen 2 and even the hackability with firecore didn't make up for all the issues I had. I knew within 5 minutes of using my Roku 3 that I had made the right decision (plus I sold the atv on ebay for a hefty markup so it actually paid to make the mistake).
Do you notice that streaming anything over in-home sharing is just plain broken? I've got everything in the house talking on 802.11n but trying to play a movie off the Mac just...takes....forever...to buffer?