I am currently on a business trip to Japan and have been using VOIP through FWD to call the office on the 800 number. It works great. I had a couple of problems though, e.g. The Z would go into suspend mode after 5 minutes of talking and would require a reboot to get everything working again. Fixed that by upping the setting in the lighting applet , and you really can't have anything else going or your sound will start crackling. No multitasking while using it, no touching the screen...
Other than that this is great. I hang out in the Starbucks, talking to the office on the Z:)