I have one that I've used quite a bit, and am pretty happy with the results. I do need to think about changing out the media though. I bought the green ceramic media from HF along with the tumbler, and while it does a decent job, I think there are probably better options out there, so I will probably go with something else in the future.
Untitled by AR Custom Knives (Andrew Riley), on Flickr
Here's an example of some titanium I finished using the tumbler. It's a little blurry, but you get the idea.
I just made one , had an old spare 1x42 motor , some pillow blocks , a 14" length of 4" pvc......
no media tumbler in the immediate area so I went to Home Depot and bought a couple 12" sq kitchen ceramic tiles , broke em up into pieces, an acid etch , sprayed the inside with wd40 and it worked very well , including the motor about a $40 investment , will take and post a pic if you like..."
what are the benefits to a tumbler vs a blast cabinet?
I've never used one but have been thinking about getting one. I have one question. If you do small to medium sized full tang blades would the abrasive round the tangs enough to cause problems when fitting the handle scales?