I have about 75 miles in the FE3. The laces are much better. I didn't like the thick laces of the v2 or Symmetros. The upper is an improvement over v2. It is thinner and feels less restrictive , but still keeps the foot locked down well enough. It feels like it has more room than the v2, but I did go a half size down in the v2 and am true to size in the FE3. So I am comparing different sizes technically.
The FE3 definitely feels bouncier than previous versions. The heel to toe transition feels very smooth due to the heel bevel, i think. I feel more comfortable picking up the pace in these vs previous versions, although it still isn't a workout shoe for me. Shoes like the Zoom Fly FK, Endorphin Speed, Tempo NEXT% are my preferred WO shoes.
I agree that the Symmetros is only an OK shoe. I use it mostly for recovery runs and easy runs when I feel I need more cushioning. The FE3 >>> Symmetros. The actual weight difference isn't huge, but the FE3 just feels much lighter and less clunky on the foot.
In Reebok's line I think the Floatride Panthea might be a more stable shoe. The Floatride+ (PEBA) foam provides good energy return and the EVA rim and lower to ground feel makes the shoe feel pretty stable and responsive.