Well, I finally had a chance to try the Maxwell free plugin. I like it! The user interface is great, and I like the preset material types. The adjustments that I want to make are all there - environment settings, material reflections, etc. In a few tests, it is actually not as slow as I feared compared to vray. I did try some interior daylit scenes, and while the speed is not too far off, the output quality is significantly more noisy with Maxwell. Overall, I like the lighting quality better than twilight, but I didn't see a whole lot of difference compared to vray. Of course, with vray, it is much more complicated to control material qualities, so it would be more difficult for a newbie to use out of the box.
In any case, it was nice to try, and I can certainly recommend it to those looking. For me though, Maxwell doesn't appear to offer anything that I can't get with vray.