Yeah, I think this is a terrific thing, especially for systems which require (potentially) complex configuration to get up and running. If you can ship a working VM image that you just "boot and go" it makes it far easier to get a system up and running for evaluation / analysis ( at a minimum). I believe that if you want people to evaluate your software and see the value in it, you need to make it as easy as possible for them to get it deployed and working so they can give it a spin.
I wouldn't make it the only means of distribution, but it's something I think many software projects should make available. I'm planning to (eventually, when I can find time) do a virtual appliance distribution of my own project. So yeah, I'm definitely on-board with this concept.
That said, I don't think having a VA distribution obviates the need to make it as easy as possible to build, deploy and configure the system via other methods. Building from source, for example. I'd still try to do as much as possible to make the source download, build, deploy, configure stuff as easy as possible.
Edit: also, just to be clear... I'm talking about this in general / conceptual terms only. Since you didn't say much (if anything) about what your actual project is or what it does, then no, I'm not actually going to download it and try it out. I'm assuming you were asking this in the context of "Would you recommend that I make this available to people who are already interested in my project and visit the website looking for a download" as opposed to "would you, Stackexchange User $FOO, want to download this appliance and try it out?"