I've actually just started re-using over the last few weeks after a winter break, due to me being a fair weather cyclist, rather than any issue with the kit!
Seems to be working fine, I'm pleased to say.
The only issue I have had, was when the elastic band holding the cadence sensor snapped mid cycle, so it fell off. Soon noticed as the motor stops giving you assistance, but it was as I was crossing a small side road, so could have been a disaster if a car had run over it, or I was crossing a drain!)
(There was a sharp edge on the pedal arm, which was the cause, but I guess it is worth keeping an eye on in general, as every time it needs recharging, which is supposed to be every 80 hours or so, the band gets stretched as you remove it, so they will eventually weaken, particularly as they age)
I'll probably get a velcro strap to wrap around the sensor and pedal arm at some point for extra security, but that's just me being extra cautious.
It works brilliantly on a flattish ride, and I can maintain a 16-17 mph ave speed which is pretty much my max based on bike, gears, cadence etc) without too much effort, and allows me to go faster than that without motor assistance, or noticeable engine drag if I want.
It still makes you work to climb a step incline, which is to be expected based on the motor output, but the assistance is still a big help on such climbs!
Either way, the assistance is pretty much instant as soon as you turn the pedal, and just feels very natural.
I like the fact I still need to pedal and make some effort, which I can adjust based on the assistance level selected as fitness improves. Of coursed if you wanted to climb hills with no effort, you'd want to get a throttle assist model with a bigger motor I suppose
I tend not to use the Vekkit app much, as it is based on km and kph, and I'm used to miles and mph here in the UK. A while back Pavel suggested they were going to add mph support to the app, but I've not seen that update yet.
You can happily ride the bike, and adjust the assistance levels with the handlebar remote with the 0/30/70/100% selections that it offers - the app just allows finer adjustment in 10% increments, and it keeps a log of your ride history if you like that sort of thing.