Well, I was skeptical and it took a while, but I finally went out and got a K&N air filter and dropped it in this afternoon. I have not modified the stock intake in any way but did notice a nice difference nonetheless. There is a little less lag than before, most noticeably at the low end. It seems to not have to work quite as hard and the power comes on smoother. It doesn't make a huge difference, but it's nice and has certainly made the VX a bit more fun to drive. So it's definitely worth it in my book. I know it's not a cheap air filter, but I wanted to toss in my endorsement because I'm definitely happy with the purchase.
By the way, the VX uses K&N air filter #33-2064.