Is Millett a good scope for my Bushy?

There are plenty of good scopes out there. Take a look at the Weaver Grand Slam series, the Nikon Monarch series, or the Bushnell Elite 3200, or 4200 series scopes; none of them are all that expensive, and all of them are good quality.

A scope will show you just how well your AR will shoot.

I put a ARMALITE scope mount on my 20" A3, and I bought a TASCO EXP scope on closeout, with a big 42mm x 54mm oval lense, and it clears the front handguard by about 1/8".

I'm still not sure about the target knobs on it, I simply sighted it dead-on at 100 yards with 45 gr JHP. In theory, I should be able to look at a prarie dog at 250 yards, click the top knob x-number of clicks and be dead-on, but I haven't tried it yet.

m.man, I'm guessing your AR probably has a 1:9 twist barrel (?) and if so I would also try some 62grn bullets when you test for accuracy.
(Just a suggestion.)

If you have the bucks and you want the best scope money can buy, then get you a Leupold.  Preferrably the Vari X III models.

What kind of 62 grain ammo do you like?

I've got some Q3131 Ammo that shoots well, and I have some PMC 55 gr ball ammo, that is hit & miss on the accuracy end, and I've got some WW 45 gr JHP thats shoots consistently well.

Some of the PMC shot into about an inch, but some of it was terrible, with very erratic groups.