Theres not much stuff out there regarding User Profile upgrade yet, but technet dont report any specific considerations beside if you use choice lists, you should remap these later to Managed Metadata Service tags if you choose in-place upgrade and if you use db attach (recommended) you should create MMS before so it can be mapped during upgrade.
Remember also that most of your User Profile Data probably are stored in AD or secondary data sources (BDC, now BCS).
You should recreate My Site host from scratch tho, since there is no upgrade path for My Sites (that im aware of), since it contains alot of new wiring especially for colleagues.
More info on migrating SA's
The most important advice i can give you regarding upgrade is TEST your upgrade before you go anywhere near your production farm. Create a virtual test environment where you can do trial upgrades and pre-upgrade check etc.
You might find my white paper on upgrading SharePoint 2010 usefull too.
Joel Oleson also got alot of info on his blog and in his book (that i am co-authoring)
Im not sure regarding audiences, but as long as AD is the same you should be good. If all else fails you should be able to extract both audiences and user profile fields that are filled in by end users programmatically in for example an xml file and import fields and values again. On codeplex you will find tools for doing this between SharePoint 2007 sites that with smaller modifications should work for SharePoint 2010 as well:
SharePoint Audience Migration http://audiencemigration.codeplex.com/
Migrate User Profile values http://migrateupvalues.codeplex.com/ (by me :-)
SharePoint 2007 Shared Services Provider User Profile Property Replicator http://mossprofilereplicate.codeplex.com/