In my opinion a well informed article albeit all the above comments are valid - there are more fish in the sea...and not ALL from your side of the Pond.
Go be our guest take a look at Networker Business/Enterprise Unified Communications. We just starting to kick a bit o' *** o'er here and would love to o'er there!
Networker = Secure, recorded IM, eMeeting, built-in Softphone (eat your heart out Skype), RSS reader, secure links vault and corporate push, Public IM gateways, AV as standard, Mobile clients (Blackberry and J2ME), WebIM and Installed Client access option and all networks delivered hosted SaaS that you control or (if you are big enough) deployed system.
No firewall issues, boundaries are exactly what your
organization wants them to be, (sorry MS LCS) control is whoever you set to administrate it, accountability and auditing as standard capabilities means if people misbehave on Public IM they can be restricted to Networker.
http/www.presence-networks.net
Deployment and provisioning for 1000 users? Give us a couple of days to make sure your logo looks nice and the notifications are exactly as YOU want them and then a day to train your IT people to manage it.
Authentication, control, accountability and security...welcome to Presence Networks Networker environment
50 - 500,000. So by all means be our guest for a test account and drop us a note if you want a pilot network set-up. Go on you might even like it!