You are actually looking for a directv ready or rvu tv. The only downside is you still need a coax to that tv for a deca. You need to have a bb deca on your dtv install. And rvu is not compatible with 3d programming at this time. Oh and you still pay a monthly fee for it.
Yes. There is significant lag over having a normal client. I used to be an advocate of it for the lack of needing a box visible but you don't need the box visible with an RF remote and the C41s come standard with an RF remote.
The other down side is when the rvu tv goes out you have to replace it with another rvu tv. I would rather have a client that I can connect even to a temporary tv until budgeting allows to replace.
Yep, a dumb TV is the smart buy. You want the smart stuff, buy the smart stuff as addons.
If you're old guy like me, you'll remember when your folks bought the console TV with the HiFi Radio - the next TV always sat on the console because the HiFi still worked.