I've had an Alien Cruiser for a couple of months and will be doing a full review after a few hundred miles. However, initial impressions are that it's a pretty competent beast. Derestricted it zips along on the throttle at about 18mph on the flat (for some reason the pedelec maxes out at 14mph or thereabouts). With moderate rider effort the bike will climb steep hills quite well (and I live in mountainous Sheffield). The style of the bike is certainly eye-catching and it has a few nice features: the battery locks neatly into the pannier rack and is invisible with panniers on; the indicators are surprisingly useful, for example they enable you to throttle and signal right at the same time.
There have been a few niggles, though. The aluminium frame and fork mean the ride is a little harsh (a suspension seatpost has helped). I had an electrical problem due to the original design of the controller box -- not a problem now as the design has been revised to house the controller/electrics in a triangular bag attached to the frame. The original gear twist shifter was hopeless; I replaced it with a Shimano-compatible SRAM twist shifter for about £9 from Wiggle and it's been great since (another forum member had to do exactly the same thing, so it's not just my experience). The wheels as supplied were so untrue it just wasn't funny. The bike is in my local shop at the moment who are trying to sort that out for me, made more difficult by the fact that there is no easy way to get the front wheel off.
So in summary, generally good but not without its problems, as you might expect for the low price. The important parts, i.e. the battery/controller/motor, seem good quality; some of the other components slightly less so, but these are easily upgradeable. I have found Bob from Alien to be good at responding to queries and problems, although he does only deal via email.
I'm happy to respond to PMs if anyone has any questions.
Greg