If you aren't opposed to applying DOF in post and have Photoshop, you can do the following:

1. Have Vue save a separate depth map when you render your scene (in render options).
2. In Photoshop, open the depth map, select all and hit copy.
3. Then open the rendered scene, select the channels palette and click 'new channel'
4. Paste the depth map into the new channel and rename it or remember what it defaulted to (probably Alpha 1 or 2).
5. Click the RGB channel to reveal the complete render and then go Filter>Blur>Lens Blur
6. In the depth map field, select your new alpha channel from #4 above
7. Tweak the blur focal distance and radius to taste and when you're happy with the preview, his ok.
8. Enjoy the accurate DOF and the amazing control you have over it :)

There are several other settings that you can play with as well, but those two are the ones I tend to use the most and have the most visible results. Like with anything, play around and see what you like.

I used to try and have Vue render the DOF in the image or do some really wonky gaussian blur/gradient mask stuff in post to fake it, but Stonemason turned me on to the method outlined above and I've never looked back. It allows you to really control the final image and even when pushing the DOF hard, the depth map stays accurate and keeps it on the believable side of things.