The current flavor allows (requires?) you to create a trillian account, which then manages your passwords and other accounts- in this sense, it requires one login.
It is available for multiple operating systems from windows 95 and macOS to windows server 2008 and most noteably, mobile devices - allowing you to have online presence in FB, Myspace, gchat - across multiple accounts..
The pro account allows your histories to be sync'd between devices (can be disabled), as well as removes ads on all devices you sign in on.
I've been a user of trillian for many years. Today, I purchased the full, lifetime version.
What I don't like about it:
- AOL popping up, saying I've signed in to more than one location wayy too often. Why can't I block that AIM bot?!
- The single year license is pointless, and you might as well purchase the life time for x4 more.
- Having to tweak the same preferences on each instance (turning off autoway, facebook notifications, sounds, ).
- Not easy enough to get plugins, especially skins.
- You can't depend on messages, on your mobile device: Sometimes there's a lag. it's not bad in conversation, but you should NOT expect to receive a message when the sender sends it - maybe it's different on WIFI..
What I like about it:
- Making it minimal on my desktops..
- the LAN chat feature
- one password.
- that it runs on my droid, my boss's iphone and our desktops,syncing chats which are searchable, and also lan's chat through our phones.
- It was always a bit above average, but not enough to justify a purchase. Finally, after using it for about 10 years, I figured I owed em.
It's a good program, or maybe I don't know of any alternatives.