TAAG - in my limited experience - are fine if very much 3 star.
I have no on the ground experience, but other than Rovos Rail's transfer I suspect the only other option might be a local taxi. You'll save some cash, but it will be materially more stressful and frankly if you've paid for a Rovos trip, an extra USD120 for the transfer seems money worth paying for the avoidance of hassle.