I've done a couple of upgrades, and I want to point out to everyone a few things, sorry if they are too obvious

1) The conversion takes a LONG time. Don't expect to just install the upgrade, convert the data, and be on your way.
2) You should change the Company Profile option in AR to allow more than 30 characters in the customer name
3) If you are going to use the new address format (which I strongly recommend), you will need to change every OE spec to use the new Billto and Shipto formatted address codes. Also, you will want to expand the customer name field from 30 characters to 40, and the Reference (usually used for the customer's PO) field from 12 characters to 24 on each spec.
4) Visit the OE Company Profile screen and synch the Address Option settings to those in AR Company Profile

Other pointers encouraged here...

Steve