Hi Paul,
I like the Teensy and i think you have done a good job.

I knew the Teensy from the OHM2013 - it's a fine small powerfull mcu for a cheap prise.
As i used it at home i did'nt see the trouble which i would get if i use more than on teensy.

Four a datalogger project at work i recommend the Teensy 3.1

The PC-os is Win 7 Pro 64

As i use more than one teensy at my pc - i notice some cons.

1. every teensy get it own COM number if you connect it. - nice if you connect more than one / bad if i want to program and test the teensy sequentially, for the test i need the serial connection
sugestion : special location on eeprom to activate a flag for using a default usb serial number

2. if a teensy is programmed the serial USB connection must be closed before, otherwise no serial port is seen in Arduino. sometime the serial connection port crash - you can see it also if teensy is disconnected.
sugestion: - if serial connection to teensy is open when programming requested and same rsb serial device number as before - than disconnect usb serial terminal window at programming and connect it after device and usb serial com port is recognised again....

3. programming sw - first i was surprised that at programming time the eeprom is not set to default value - if i try to know why - i see that some user wanted this exactly so... i would wish to have a clear eeprom functionality.
sugestion: button or cofiguration option to define the behavior of the flash programming( wipe /wipe not)EEprom out.....

4. bottleneck - in germany availbe Wizio820 & SD card adapter.... it seems not so usual - long time to get it....

note: if someone have interests i can share my (teensy / Wizio820 & SD card) case model

forum website suggestion:
1. picture upload: I want to upload a picture but it isnt possibe error 403 / Error #2038 - whats wrong?
2. search function: why did i get none entry if i search in your forum for "LIN" for example ( i know this post exist)..... google guides me to the right side in your forum.

As i said before you did a really good job.
I know how many time some "small improvement" can consume.....
My suggestions is no critic - its a form of respect to your work and also a way to show improvements as seen from my side other viepoint is maybe different ;-)).

Best regards,