We have not seen issues on Windows machines using Arduino 0022. The 'Board Definition File' on the product page is configured for Arduino 0022. I am not sure if 0018 or 0023 will work.
Overall, Wiring 1.0 (
http://wiring.org.co/) and Windows is probably the best option right now. You can follow the instructions here to get the Mega Pro 3.3V working with Wiring:
http://wiki.wiring.co/wiki/SparkfunHardware
FYI, Wiring is basically the same thing as arduino. you can write the same sketchs and include libraries in the same way. The Arduino IDE is actually based on the Wiring IDE.
I hope the linux/mac issue will be worked out shortly, it's probably something obvious I am missing. Keep an eye on the product page for any updates.