The Steyr AUG proved the concept had military application, but the AUG itself has proven to be less than ..optimal. At least one of the nations that adopted the AUG have since replaced it with an M16 variant.
I wanted an AUG for a long time, and handled one in a store, but in the end my choice came down to ergonomics. I don't care for crossbolt-type safeties like the AUG's (I think they are slow and awkward, whereas AR-style thumb safeties are quick and easy to flick on an off as needed), and I didn't care for the AUG's bolt release and mag release setup. I did like the AUG's quick-change barrel, though.
In a varmint rifle, the balance doesn't matter much, compared to other applications. Semi & select fire bullpups by design put the bulk of the weight to the rear of the rifle. This has pros and cons, but is generally considered to be more limiting than conventional rifles.
I've never personally used one, so I really can't say, but while they look neat, they also look awkward to me.
Having more weight out front certainly does steady a gun more for longer-range shooting, at least from unbraced positions. The less mass out front, the easier the muzzle is to disturb, and vice versa.
I personally find the Tavor's more rearward balance less awkward than an AR in fast transitions, switching shoulders, magazine changes (when not prone), and anytime you are running the charging handle or need to manipulate something else with your support hand (doorknob, cell phone, whatever). So again, I think it is good to figure out what niche you are looking to fill. AUG's and Tavors are better HD guns than they are long-range guns; you won't see any of them in F-class benchrest, but there are plenty of heavy-barrel AR's playing in that field. Different horses for different courses...although I have read that the AUG is a little more accurate than the Tavor.
Also, keep in mind that the best comparison to an AUG or a Tavor are other 27"-28" rifles (of which most are SBR's). A 10" AR will have a less-forward weight balance than a 16" does, and a 10" AR with a red dot won't be much more accurate than a Tavor at 400+ yards, with worse ballistics at all distances.
There is one big downside to the Tavor, AUG, and other bullpups that hasn't been mentioned yet, and that is cost. The AR benefits from being produced in the USA by probably 50+ companies all competing with each other on cost, from 50+ years of production experience, and from economies of scale since it is the most popular centerfire rifle on the market. The AUG and Tavor both cost upwards of $1500 new, and while you get a lot of neat features (CHF 1:7 barrel and tritium BUIS on the Tavor, for example), you can buy an AR with those features for $500-$700 less. The Tavor's gas system also vents excess gas from the stock vents, making them not the best choice for shooting with a sound suppressor for those who own them. But other than that, I think they are great little rifles.