This week, Ableton has released Live 8.4 beta. This new (trial)version of Live offers 64-bit support, which means that the 4 gigabyte memory ceiling finally is broken. This is especially good news for those using mega large amounts of audio files and samples in their Live sets. Some users also report a significant performance improvement, see the comments under this article of Create Digital Music.
Less good news is that users of Max for Live and The Bridge should temporarily postpone the upgrade to 64-bit. These programs have only 32-bit support. Users of 32-bit plug-ins have to use a bridge adapter, a piece of software which communicates with the 64-bit program.