This has been a question asked by several customers. I just stumbled across this new useful feature comparison matrix on TechNet. I pasted them in below.
Matrix is here on TechNet.
good matrix - very useful - but where is the mention of Microsoft's Persistent Group Chat. It may not be used by all but those of us who do use it live on it. I can do without 99.9% of all the other elements that are covered but not without GC.
Good point Gav. GC is not getting the attention it deserves however in this matrix there would not be a lot here. I will post on what is new with GC in Lync 2010 next week.