I haven't had any problems with the cheap ebay ones, and I've dealt with 3 so far. I guess you get lucky sometimes.

Looks like a great setup with the Kindle, Mike! I put Torque on my BB Playbook through a similar way a while ago, but haven't really tried it to see if it worked. Torque Pro is one of the best apps I ever bought.

The basic BT units utilizing ELM327 OBD to UART interpreters are not too bad for needing to monitor a few PID'*, in my experiences when I try to monitor/log data on more than a few basic PID'*, the data seems lagged quite a bit.
I think the best dongles to buy are the ones utilizing the newer STN1110 OBD to UART interpreter, it is a bit faster IC.
Below is a PDF comparison, ELM327 and STN1110 are backwards compatible.
http://www.scantool.net/scantool/dow..._vs_elm327.pdf

I am not sure if the PLX KIWI uses ELM327, or STN1110, I tried to search for data on which IC they use, but had no luck.

This is the dongle I am going to buy when I can afford to, it definitely utilizes a STN1110 IC.
ScanTool.net LLC - OBDLink Scan Tool/OBD Interface - ScanTool.net

I currently use a chap ELM327 IC BT dongle I bought from E-Bay, and it does work ok for a few PID'*, but I have to use roqyBT4, and roqyOBD4, to get it to communicate with the ScanXL Pro app I run on my I-Phone.
When I am able to get the OBDLink dongle I'll try to compare data transfer speeds, if I can think of a good way to accurately do so.

i use one of the cheap elm327 ones and it seemed fine initially for monitoring some data like trans temp, and fuel trims. always took 4 times longer than my standard scanner to clear and read codes though. and now it just seems incredibly slow when you are trying to read advance or fuel trim. the phone is fast, thats not the problem