Once in a while while chatting I'll send files. In Thunderbird I can't. Also that would be a nice plug for FileLink, specially when sending to clients that won't receive file (gtalk on android for instance).
Doing this with FileLink is a must! File transfer over instant messaging is notoriously bad (meaning an awful user experience...). To lay out some of the work involved in this: 1. The chat/ backend would need to be updated to know when to initiate/receive a file transfer. 2. UI would need to be created to initiate/receive file transfers + handling of downloading files (although this could be handled however Thunderbird deals with attachments, most likely). 3. The protocol implementations would need to be updated to support file transfers (with a fallback to FileLink?) 3a. XMPP needs to implement XEP-96 SI File Transfer  or XEP-234 Jingle File Transfer  (I don't know which of these is "more supported" or if both should be supported). (Bug 729544 might be of some help for the Jingle option...?) 3b. IRC needs to implement some of the various DCC methods: SEND, FILE , Turbo DCC , REVERSE , RSEND [??? no source], RESUME . I'm sure there's more out there too.  Has a full list/comparison. :) I have some partial DCC code around somewhere...  http://xmpp.org/extensions/xep-0096.html  http://xmpp.org/extensions/xep-0234.html  http://www.irchelp.org/irchelp/rfc/dccspec.html  http://www.visualirc.net/tech-tdcc.php  http://cvs.epicsol.org/cgi/viewcvs.cgi/epic5/doc/DCC_REVERSE?rev=1.4  http://www.team-clanx.org/help/dccresum.txt  http://www.kvirc.de/docu/doc_dcc_connection.html [Instantbird bug] https://bugzilla.instantbird.org/show_bug.cgi?id=9