I have the OKI data 610 and it works great. The toner in the OKI data is way better than the ones in the HP and the Brothers. When I did a test on all three the color was way more vibrant and the hand was softer. It also has good resistance to wash. Plus it has a bypass tray so your paper feeds in straight which is great.
Also the fuser is way more constant than the HP and Brother which is important when printing on heat transfer paper.
I use the Image Clip laser dark self weeding paper, I like this stuff, soft hand and does not crack. My tests shirts are going on 16 washes and only a slight fading and still no cracking.
I use when I have small runs of 20 t-shirts or less to do.
This is the machine I have:
http://www.youtube.com/watch?v=vsvJUm4ZMqo