Yes, the slime is a great idea! My one also came with a problem out of the box, which was that one of the buttons on the stem wouldn't pop out properly. On attempting to extract it with a pen as advised in the manual, I quickly lost it totally inside
Luckily I was able to get a quick replacement for the bike from Selfridges, as I didn't fancy dismantling it myself or waiting 28 days for a repair.
So I guess it's typical Sinclair style with a few "teething" problems. But lets hope it sells well, to encourage future development and also new ideas from other manufacturers!