Major bugs fixed:
- Crash on outgoing server link attempt.
- Crash on boot with bind/listen errors.
- GLINE/KLINE/.. were refusing perfectly OK bans.
- Possible freeze when SSL client is connecting.
- Remote includes were broken.
- Compile problems on OpenBSD.
- SSLv3 is now disabled for security. Pretty much all clients supports TLS so this shouldn't be a problem.
- Support for ECDHE has been added to provide forward secrecy
- If you are linking a 3.2.x with a 3.4.x server, with SSL enabled, then you need at least version 188.8.131.52 on the 3.2.x side (earlier versions used an incorrect OpenSSL API call and therefore supported SSLv3 only. Yeah, silly, we know. We fixed it in May 2014 but some people may still be using old versions).
- If upgrading from previous beta's then you'll have to run './unrealircd upgrade-conf' or change your listen blocks manually. This because we changed the listen block syntax to get rid of the strange  brackets in IPv6 listen blocks.
Full release notes are available here. Be sure to read the release notes if you are trying out UnrealIRCd 3.4 and are currently on 3.2. It contains important information on the new location of files, configuration format, and how to automatically convert your unrealircd.conf to 3.4.x format.
As always, you can download UnrealIRCd from https://www.unrealircd.org/
EDIT: Downloads were replaced on 07-09-2015 11:50 UTC, so about 24hrs after the initial announcement on the forums and main site, but before the announcement to the mailing lists. Reason for this change was another server crash and /GLINE etc. not working. Only 15 users downloaded the broken/unfixed version.