I mostly use ESFile Explorer. I connect to my computer over wifi using the IP address. Then I can simply brows files on my computer and copy and past them to the Xoom.
Yeah common files work well with bluetooth so far, I just got swiftp and tried it out worked very well. Dropbox was ok nothing great for me. And usb was good for large files.
I use Dropbox, the USB cord, and Amazon Cloud for music. I did use Doubletwist AirSync for a bit but I rarely sync music to my device anymore, thanks to Amazon Cloud music.
dropbox here for large and small files.....if you're on the same router, the transfers are nearly instantaneous....large files only slow me down when I don't have both my desktop and xoom on the same router
Wifi File Explorer App is great.. it runs a local server off your Xoom and lets you browse/upload files via your desktop browser. Works great and involves no cables.
Alternately, I use esFile Explorer to "pull" files to my xoom from my local server.