The positive thing of Arc being implemented in top of MzScheme is that this way you can easily modify the core language and try new features without messing with assembly or virtual machines, but in the long run an independent implementation seems to me inevitable. Arc2c is moving this way and I think it will eventually abstract over C, maybe by targeting a general bytecode that can be translated to C, to assembly or interpreted by a VM (this is I think what SNAP is supposed to do).
I constantly see comments bemoaning the lack of progress in defining new language ideas in Arc. I don't say I agree 100% with this complaint, although probably the closest that the community has come to this is with hcase.
And of course pg gives library design the same status as language design -- or Arc does, by being so damned flexible. It's not as though Arc is standing still.
But really, the thing that's going to advance the language will be when we use Arc to make things! And that takes some time, and the things we want to make may not be all that important but they'll be interesting to us.
And so while Arc's built-on-PLT status is an obvious hindrance to winning language pissing matches, it means that little is preventing us from doing very interesting things. In fact, that's why FFI's have been such an exciting area of discussion; many of us were limping along with fun little pet projects in another language that wasn't ideal but that had a convenient interface to a couple of C libraries.
In my case, ruby has a good interface to Gosu (for smooth, fast, trouble-free operations on images, even big ones, abstracting away a good chunk of opengl use cases while still letting you use opengl where you want to) and chipmunk (for relatively pain-free 2D physics), and so I made a little screen-saver that has my photographs, mixed with random pg whodehouse quotes from drones.com, tumbling down the screen waterfall-style, and then set about cooking my own code. I got it down to under 100 lines with room for improvement.
(I was living in a fishing village in pacific south america for the last 6 months, with nothing but a $300 windows vista craptop a friend loaned me, so my projects were necessarily of the silly, one-off, only-until-the-surf-gets-good-again variety. I just got back a week ago.)
At the moment, I'm mulling over redoing the same project in Arc, and so my first step is figuring out how to use Chipmunk and Gosu in PLT Scheme. I've never used a C lib from scheme before, so this could be educational.
But I can at least consider doing this project in Arc, in the short-term, because it's implemented on top of PLT. Bad for winning a pissing contest, good for hacking.
