I hate Microsloth, this morning I booted up to a message saying "We have signed you out of Skype because you're using an outdated version"  with a link to download and get a Microsloth account that I don't want nor need.

Typical of Microsloth, force their updates regardless of your needs. The version I and a few others have been using is the last one before MS took it over and started adding unnecessary bells, whistles and Ads, it ain't broke so why this sudden need to fix it?

Any suggestions for a simple IM with file transfer capability, not worried about voice or camera?

No, but I'm sure members will 

search found
http://www.pocket-lint.com/news/131512-5-best-alternatives-to-skype-apps-with-im-video-calls-and-file-sharing

hope this helps
tony

We've used Lync, Slack, Skype and HipChat at work, Slack and HipChat are both pretty good.

Or you could just y'know... use Skype?