There are 2 limitations to the AirTV 2:
1) Only 2 devices can "stream"/record local channels at the same time (can be different channels). If you are planning on recording local channels (See #2) it effects the number of streams available for watching as a recording takes 1 of the available tuners. So AirTV 2 can record 2, watch 1/record 1, or watch 2 at the same time. The AirTV Anywhere device, also on special with Sling, but $99, has 4 tuners so you can watch/record 4.
2) There is no DVR functionality built in for local channels (the sling built in DVR will not record local channels), but you can hook up a 1-2 Tb USB hard disk drive to the AirtTV 2 then you can record up to 200 hours of local TV. The AirTV Anywhere device has 1 Tb built-in for DVR.
Edit: There are also other devices that allow you to hook up your HD antenna to your wi-fi network. One is a Tablo that has various device options. You use their app and hook up a USB drive for recording (I don't think the newer versions have a built-in HDD, but I am not sure). No integration with Sling and more $. The nice thing about the Tablo is you have a lot more functionality with how you setup the device (AirTV is pretty much plug and play - no customization). One negative for Tablo is that you need to pay for the the Guide for shows (with AirTV it's built into the sling app) to see what's playing so an additional monthly charge or a large lifetime subscription purchase. I have also tried the HDHomerun device (first gen) and I believe the main issue with them is they don't use wifi and require an ethernet connection to your network (an issue since my wifi and antenna have never been on the same floor). The other issue is how they DVR shows as I believe they require a network storage device, but I believe some of the newer versions have a built-in DVR/HDD. I also hated the interface as the AirTV and Tablo are 10X better. Overall the easiest and cheapest to use would be the AirTV devices (mostly as Sling bought them several years ago to allow local channel access).