The online system is pretty easy to use and changes take place within seconds in most cases.
However, I have run across some issues going from iDen to CDMA. Most notable is that you will lose ALL voicemail and will have to set it back up each time. Also, Iden SMS is terrible, if you communicate with SMS be prepared to have significant SMS delays. not to mention the poor data speeds. Beyond that, there are provision delays from time to time and it could take hours for the switch to go through when you do an Iden to CDMA switch. I actually had on that took about 36 hours. Granted, the exception to the rule, but considering I do about 100 esn swaps a month, I have some experience with the system. These problems don't happen NEARLY as often as a CDMA/CDMA trade. My advice, sell the iden, buy a cheap CDMA device.