My screen was horribly scratched and you could feel the scratches all over. So bad that you could barely read the screen through the scratches when in direct sunlight. So, first I tried PlastX.. like 6 coats, made little to no difference, then I tried some car polish (Sonus SFX-1) and still no difference. So I tried a dremel at 5000rpm with the sfx-1, took off a tiny bit of the top layer, still no real improvement.
Finally, I tried what I thought would either work or destroy my lens, wet sanding. Used some 2000 grit and polished off the top layer of the lens. There seems to be a top soft layer that can't really be sanded, scars up horribly. But, I found underneath is a higer quality plastic that scuffs very little when sanded. It took me almost 3 full hours to sand the lens down to this layer. I then did 2 coats of PlastX applied by hand and now the lens is almost perfect. The lens looks practically new! The only issue is the lens has ripples in it (only viewable from almost a 90 degree angle to the screen. Side effect of uneven polishing by hand. Now that I have removed the soft plastic, I am pretty sure I will need one of those invisible shields for the rest of the unit's life.
So, if you have a scratched up lens on your 60 series unit, it is possible to get them out, it just requires many hours of work.