With our upcoming Office365 cloud service, Lync Online will be a part of the offering. I have had a few education customers ask me what the differences will be. I found this useful matrix (note: this is a Lync Online beta feature matrix and subject to change):
From the Beta Lync Online Service description document here. Note: there is also a matrix for Beta Exchange 2010 Online vs. Exchange 2010 on prem comparison matrix.
How about federation / PIC - is this is part of the new Office 365 offering?
Dennis, This is on the roadmap for delivery with Office 365.
Enterprise Voice is definitely one of the deciding factors for larger organizations. www.sourcesolutionsco.com/.../office365-why-go-on-premise
This chart is a good visual of that. Thanks!