Hey Duncan.
Well... Two months later, the Tubes have been relegated to the pile for day to day wearing. As basic trainers, they're amazingly light and comfy. As actual running shoes, they didn't suit me at all.
I went out on a couple of short runs and they felt okay, but I found it hard to get them to lace up tight enough. As someone else already said, when cornering etc they felt rather flimsy and like my foot was shifting around inside the shoe. I put an old pair of Adidas insoles in them, under the insole that was already there, and that helped make them feel snugger round my feet. Then I went out on a 10 mile hill run in them (unplanned - the mountain goats in my running club just took an impromptu detour one night!) and while running uphill started to feel burning pains on the insides of my lower legs. The pain subsided after the run but subsequently developed into shinsplints which held me back for the next month or so. I didn't run in the Tubes again but have kept them for everyday wearing.
I'm not blaming the Tubes for my shin splints, as I was already overdoing it in other old trainers that were long overdue replacement, but I do think they contributed slightly. After slow-mo video analysis, I found out that one of my feet splays out very slightly when running, which puts strain on my ankle and shin muscle. It's not pronation and while I'm definitely a neutral runner, I've been advised to stick with shoes that are quite firm around the heel, which the Tubes definitely aren't due to their over-squishy soles.
So I suppose getting them and finding them unsuitable actually did me a favour, as it highlighted a small biomechanical problem that I didn't know I had and that could have ended up doing me more damage if it had niggled away for ages and I'd passed it off as usual minor running aches and pains.
Anyway, I've since bought two more pairs of Cumulus (the love affair continues, LOL!) and a pair of Brooks Ghost as recommended by my usual shoe fitter after watching me running in slow-mo in several different pairs of trainers.
I suppose the Tubes might suit smaller, lighter, and biomechanically perfect runners. If that's you and fancy giving them a go, good luck!