I recently purchased a Sprint PC-5740 .  The card's compatibility doesn't list Linux, but I felt like giving it a try anyway.  A quick search through google brought me to Ken Kinder's EVDO PC-5740 page.  You'll find quite a bit of information at Ken's site, but it didn't exactly depict my findings, so I'll document my personal findinds here.

My computer

I have an HP Pavilion ze4904us and as of this writing I am running Mandriva 2006.

Windows First

The sales person at the Sprint store mentioned that I would have to activate the card before I could use it, so I assumed that this process of activation could only take place with the Sprint software within Windows.   

On to a better OS

Once the card was activated through the Sprint software, getting it to work under Linux was cake. Following along with Ken's step-by-step procedure, I inserted the card and loaded the appropriate module.

modeprobe usbserial vendor=0x106c product=0x3701

Here is where my experience differs from Ken's.  To quote Ken, "If all goes well, you should have a file called /dev/ttyACM0:"  Things weren't going so well for me at this point.

ls:  /dev/ttyACM0: No such file or directory

Through a little bit of deductive reasoning I found the modem at /dev/ttyUSB0

kppp 

For ease of use and to prove that you don't have to know the command line to use Linux, I decided to use kppp to setup the connection.  Just go through the regular kppp setup and set the modem to /dev/ttyUSB0 and set the modem init string to ATZ.

With SprintPCS you can get your username from the Sprint software in the diagnostic section.  No, there is no password.  Dial #777.

Performance

A quick download speed test on CNET revealed roughly 300kbps.