I've just done the same. Can't help with the voice commands but I'll throw in two other issues I've found. One is that the display doesn't show true speed any more, but just indicates the local speed limit which changes colour if you exceed it.
The other is a bit more complex. On the old model, the live traffic system (if you paid for the subscription) updated via a GSM link built into the car. The new version requires you to have a smartphone which can set up a wifi hotspot, so the updates come in using your phones data allowance (not a large amount of data, fortunately). It may be my phone (HTC One) but this seems very flaky, plus you can't run a wifi hotspot and leave the normal wifi on at the same time. It's one or the other and you have to remember to switch between the two.
The dealer is also going to look at mine as it keeps dropping out and rebooting; it did it three times in one 40 min journey on Sunday. Once, it rebooted with a screen showing a message saying no navigation system was installed and replaced the map with a digital compass!
Alan