One more tip: Gmail has a "merge duplicate contacts" feature that's a huge time saver during the cleanup step.
I've used this approach since gmail added supported the active sync protocol. It's work out quite well.
The funny thing is that you can do that on Android by default.
I did this in the past, however I didn't wipe the existing iPhone contacts and therefore they didn't sync properly to my Google contacts. Now that I'm moved on to Android, is there any way for me to get my contacts out of iCloud?
Hmmm it never occurred to me to do a write up of this process. And it's funny, because I did exactly the same thing in the same order.
Yes, this process works quite well and cleaning up your gmail contacts is a pain, but most important step.