thats a great price - i tested the smart ebike for a couple of days when i was first looking for a bike, and if someone is looking for a town commuter bike its great - quiet and the belt drive is a great system. Range was good (though nowhere near claimed - just like everyone else) you can buy suspension forks as an optional extra for not much money iirc, but for around town, these are very good. It's a nicely proportioned frame, and hauled my 110kg's around well, also display is nice.
The suspension issue is different to standard bikes, i think the frame design has some give in it, and that helps smooth out the bumps (note i'm guessing) but its a very different ride to a bicycle.
Its worth riding one because the experience of the belt drive is lovely compared to chain drive systems....My main issues was the price (but i guess the merc dealers have to pay for their fancy showrooms somehow), and also smarts history of delivering things that look great and then fall down later (i've owned four models of smart cars and still own one, and they are great, but quirky to say the least) - I think for 1300 quid for a basically as new bike its a steal compared to the cost of a new one, as long as you aren't off road or rural with too many hills, but i think you'd need to get someone who's ridden one, as comparitively on paper it doesn't seem a great spec for the money)
good luck with the sale!