arduino pro voltage warning

From https://www.sparkfun.com/products/11114 -
"The Arduino Pro series is meant for users that understand the limitations of system voltage (3.3V), lack of connectors, and USB off board."

What do they mean by "users that understand the limitations of system voltage"? Is that to say that you simply stick to 3.3v everywhere for this piece, or is there something more complex that I am missing here?

Is that to say that you simply stick to 3.3v everywhere for this piece,

Yes that is basically it, don't expect to connect directly with 5V things. For example most alpha numeric LCDs are 5V so if you want to use them you need a logic voltage converter for any signals coming back from it.

blah44:
What do they mean by "users that understand the limitations of system voltage"? Is that to say that you simply stick to 3.3v everywhere for this piece, or is there something more complex that I am missing here?

There's lots of 5V devices that won't work with it.

Usually the HD44780-based displays work just fine on 3.3V supply and signals, but you need a negative supply voltage for the contrast.

// Per.