I have had no problems whatsoever. Do you use a program to sync your mail, calendar, and contacts? If you do, there should be no problem getting all the info back onto your iPad. My Google calendar updates onto my iPad faster than I can say, "Google Calendar - Go!"
And, BTW, I find the update to 4.2.1 SO wonderful. I have not had a chance yet to see which programs will continue updating in the background for TRUE multitasking and which ones are just there for faster app switching. Now, if it only had Flash....