Lync is far from being WebEx, must less TelePresence, when it comes to multimedia conference, but it does represent a "unified communications for the rest of us" offering for small businesses, offering a balance of consumer and enterprise features with appropriate IT oversight.
But it's the Office 365 monthly subscription model that really makes it shine as part of the larger suite. Unified communications is one of those deployments that many businesses would benefit from but never seem to get around to because of architectural complexity and expense. Moving it from capex to opex make it a much more achievable goal.
However Lync is not perfect for the enterprise on the go, especially not today. For businesses that have standardized on Windows Phone 7 (both of you), you're in good shape. For the rest of us, getting Lynced up on the go may be a bit more of a challenge. There's a BlackBerry version available as well. Microsoft has pledged support for a variety of other platforms, including iOS and Android, by the end of the year. Keep in mind, though, this is a Microsoft-offered timeline, and those have been known to change without notice. Windows Vista, anybody?
There are other differentiators for Office 365 as well, with SharePoint clearly chief among them. Microsoft's polarizing intranet portal software is the company's fastest product ever to $1 billion in revenues, and Microsoft seems to be constantly reminding its partners that it has more demand for SharePoint deployments than it does partners to do such deployments. But on the other hand, it's been criticized as too complex for small businesses, a very powerful tool that builds that power at the expense of simplicity and usability. However, with Office 365's backend tools, perhaps things will be a little easier for the smaller customer.