One required feature is the flexible toe-ball connection (so that you can comfortably use the toes to balance when the weight is on the balls of your feet), which not every shoe without heel cushioning will provide, though some probably will.

The other important feature is "high-resolution" impact transfer - you need precise ground feedback for your muscles to compensate for an uneven terrain.

If you have (as an extreme absurd case) a super-hard graphite/plexiglass sole, then you have no cushioning, but are not likely to avoid delivering impacts to your knees even if you run on the balls of your feet.

Supposedly, Vivo Barefoot, Nike Free and Newton are as good. But I only have experience with the Vibram FiveFingers, which is why I recommended it.

I own a pair of the Merrell True Glove trainers and love them. I thought they used basically the same sole as the VFF, although obviously not with separate toes. I just couldn't buy into having plastic between my toes, or not having option of wearing some liner/socks, also since mine look more "normal" or let's say less "goofy" I can confidently wear them in any environment.

Never heard of these - I will look them up.

> I just couldn't buy into having plastic between my toes

Me neither, but I just had to try, and I actually like it, even though I don't like "toe socks" inside a regular sneaker.

> or not having option of wearing some liner/socks

There are injinji socks; but I prefer the VFFs unsocked if I can properly wash and dry them (I use socks when I don't have wash-and-dry facilities).

> since mine look more "normal" or let's say less "goofy" I can confidently wear them in any environment.

That's a definite plus. (On the other hand, if you're looking for a conversation starter, the vibrams are hard to beat!)