There are some very minor differences between CRM Online and CRM On-Premise that are worth mentioning.
The one that tripped me up yesterday was my inability to import a new report extracted from one of the new accelerators. I was thinking about running a quick test and not thinking about my rule changes in the CRM online world. Doing what I normally would do in one of my test VPC images I moved forward only to be stopped.
You can not upload custom reports into the world of Microsoft Dynamics CRM Online.
You can use the Report Wizard, the Power extraction of Dynamic Excel pivot charts and spreadsheets and much, much more so don't go screaming away. Still there are some benefits to having total control of the source.