If you want an insightful synopsis about Tello, and where it fits in the scheme of things, Andy Abramson - as usual - has it pegged - http://andyabramson.blogs.com/voipwatch/2006/01/tello_explained.html
I'll just add my two cents here. Jeff Pulver has the best timing of anyone I know in this market, and I'll say this much - announcing the Tello launch during the week of TMC sure diverted a lot of attention away from the show (perhaps his main rival), at least when the news cames out. That was pretty evident to anyone who was there. The spirit of competition is a 24/7 thing, no doubt about it!
I'm also of the view that Tello is poised raise the ante as all the big players start making big moves to marry voice with the web. VoIP Inc. getting cozy with Google is an example of what's coming now, and I'm sure we'll see more moves like this soon.
Skype has been making its own share of announcements, and I suspect they might see more doors closing now than those that are opening. As the IM platforms add their own voice apps, Skype's appeal may falter, esp if they do not adopt a more open platform. Right now, this prevents them from "federating" with other, SIP-based platforms, and perhaps more importantly, it limits their ability to penetrate the enterprise market, which is where good money can be made. Tello is all about the enterprise, and my take is they have the right vision at the right time to make all these cool applications work seamlessly with each other.