I own a TI 36x, TI 30x, TI 83, and a TI 86.  I have never had any problems with any of these calculators and I use the 36x and 86 every day.
In order to link my 83 and 86 to my computer for downloading programs I built a Parallel Port link.  It can be used in teaching to give instructions on how to use the TI graphing calculators.  This can be done by using a computer monitor to capture the calculators screen. I built it using plans similar to those found on Andrew Westfields page.  If you don't have the time or the resources to build your own I still sell them.  The one I build is pictured below.  It plugs into the parallel printer port of your computer.  You plug your Calc-to-Calc cable into it and then into your TI graphing calculator.  I charge $11 US.  I take checks, money orders, or cash.  Shipping is included by the way.  In the package you get 1) the plug which connects to your computer, 2) both paper and electronic directions for installation and the links use, 3) software to run the link, as well as a few sample programs.  The programs come on either a 3.5 or 5.25 floppy disks.  So you do not have to worry about getting stuck with a piece of junk I test the links three times before I send them to you by sending programs back and forth between my computer and calculator.  Technical support is also included.  Parts and labor are guaranteed for 1 year.  If it breaks and you did not abuse or tamper with it I will replace it free of charge.  This includes sending you a check for the return postage.     
 I can be contacted by :
email at yatko@hotmail.com,
             yatkonj@ibm.net
 fax:  (817)488-8560
snail mail:   #114,  204 E. 21st Street   Austin, TX 78705.

In correspondence please include what TI graphing calculators you will be using the link with.  Also include your mailing address.  I will be happy to answer any questions you have.

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I am back in Austin. Starting Wednsday January  12th send all correspondence to the above address.  Nicholas Yatko   #114, 204 E. 21st Street   Austin, TX 78705

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Heres is a picture of how it works.

Here are some places you can check out