the biggest ones are still to come (soon)

Thanks for taking a look at JustProto.

We are a web development company (http://desmart.com) using prototyping on daily basis with our clients. We tried quite a few tools but still needed something that matches our needs better. That's how we created just proto. As you mentioned we opened it to the world recently (Jan 2009).

As for immediate preview it's about ability to preview changes done to prototype in real time via html website (so without entering the tool)
&
in multiuser collaboration the ability to change one element by 2 users in real time (already works but we are still polishing it – should be fully functional in 2 weeks)

We believe JP is:

simple and easy to use,
fast and reliable (we really worked hard on optimizing the code:),
and immediate preview and real time multiuser online cooperation are unique from what we've seen
It is also important that you can suspend you account, without losing your projects (and have access to some features without paying monthly fee)

JP is still under heavy development so much more will come soon and [b]feedback is highly appreciated[b].

Also thanks to Jamie – we are still young tool and at the moment user feedback is crucial for us. As for your remarks
(1) we will add more elements , and there will be much more to it, but I just can't reveal it yet
(2) CTRL-C & V and CTRL -drag are implemented (works on FF and IE) please report your problem so that we can check why it does not work on your computer
(3) vide #1 we are working on it, will come soon:)
(4) it's actually not that easy but we will work on it

Any one who uses out tool please use the support>> give us feedback – it's highly appreciated
You can also reach us at support[you know what goes here ]justproto.com

You can also visit our blog on prototyping http://blog.justproto.com << still quite a few posts in English but its growing

Some things I encountered almost immediately: (1) text is not also part of a box – if you want to add a text label to a box you have to create two separate elements; (2) no easy way to duplicate elements on a page (e.g., ctrl-drag or even copy/paste); (3) no basic widgets/stencils for tabs; (4) no easy way to zoom in and out – i could do this with my browser, but that's Firefox, not JustProto.

I'm sure there are many more. It just is not ready for prime time as a useful wireframing tool imho. Not even as a free one. Why would anyone pay for this in this state?