Thanks for the input guys - I think you are both right, it's partly to do with the snow conditions and partly to do with my technique. I don't believe there is anything inherently wrong with the skis, especially as so many other people have had such a good time with theirs.
To Lilcliffy's point, the first two times I used them I did have a pretty positive experience, since then we have had a period of mild weather and this has made the conditions difficult to wax for. On the tracks it's currently slightly wet, groomed snow over harder icy stuff - certainly not ideal! I haven't had much chance to test them on fresh snow, but going off the tracks in some deeper, ungroomed snow has actually been more positive in terms of grip, so I'm reasonably confident they will be better when I take them up to the mountains.
My old Rossignols still ski nicely, but they were a beginner to intermediate level ski so it's probably allowed me to be a bit lazy and my technique hasn't needed to progress to a more dynamic style. The OT65 I have are certainly stiffer as you say, but as these are waxless they don't require much finesse to use. I will definitely have to be more conscious of my weight distribution/body position when using the Gammes, as well as learning to be a bit more aggressive when kicking.
I obviously cannot speak to your skiing style, technique, and snow-terrain conditions- but I can DEFINITELY echo your frustration with lack of grip. I simply CANNOT tolerate inadequate grip. I prep my skis such that I can kick and glide without the use of my poles.
Totally agree, I like to use my poles more for balance and rely on the ski for forward propulsion, it's been really frustrating not to have that with the Gammes.
I haven't used Klister on the Gammes, although the conditions probably warrant it right now. My aim was to use the X-skins as an alternative to messy Klister for warmer, wet snow - which definitely worked pretty well when I tried them the other day. I will trim another 1cm off the heel and see if that improves the glide a bit more.
Ultimately I bought these as a mountain ski, and have been testing them like a track ski so the problem certainly lies with me!
I will keep on with them and report back once I've got a few more miles on them!