Don,
I don't think it was to hard. The big thing is if you are migrating your custom widgets and want to use mainly Spark then you have to get rid of your repeaters and switch to data groups, which force you to develop item renderers for the datagroup. I went ahead and took the time to migrate all my widgets to the new Spark components all except for my TOC widget. I had to fix serveral things in the Beta Viewer, like data messaging, the infopopupwidget, lots of css, issues with the tooltips and header widgets appearing below docked widgets, etc.
There no time like to present to dive in as this is the direction everyone needs to go.