I am currently shopping for a coyote gun...

I think I have decided on a semi-auto .223, for various reasons (second shot, like the caliber,etc.)

I also have thought long and hard about getting an AR... I am not ussually a fan of military guns, matter-of-fact I ussually turn up my nose to "those" tables at gun shows.

Having said all this, I recently read an article lauding the AR's capabilities. I think after doing some exhaustive research I have decided on the Rock River Arms (RRA) varminter.
It has a guaranteed 100 yard 3/4 moa, a free floated barrel, and a flat receiver. MSRP = $1000

A couple of questions...
1) do you guys like that choice, why/why not?
2) What length barrel should I get and why, 18, 20, 24 inch?
3) is the RRA the best bang for the buck?
4) what scope would you mount?

Thanks in advance!