The JTAG MKIIs are not indestructible. I have 6 JTAG MKIIs. Two of them have failed, one was at least 3-4 years old. The second was 2 months old. Over the years I have also had 8-10 flat flex cables fail and a pod fail. The most recently purchased came with an extra flat flex cable.
I purchased a Chinese knockoff, it never worked.
I have a Dragon I don't use.
I would like to buy 1-2 of http://www.dhgate.com/usb-avr-jtag-ice-mk-ii-metal-box-anodised/r-ff8080812cf9abc5012cfaf3e60f6e35.html I like the metal enclosure and the fact that it uses a ribbon cable instead of the flat flex cable, but I am gun shy since the other knockoff was DOA.
I keep purchasing the real unit and have recommended on several occasions that clients do the same.