RE: Mac builds: what BlueMatt said. Despite using a Mac as my development machine, I am not a Mac developer-- I'm an old Unix developer at heart. I learned enough Windows "Win32-api" programming to create a couple of products, and I know a lot about web development, but I'm a newbie when it comes to making applications for the Mac.
RE: wallet encryption: I want encryption of wallet private keys (requiring you to enter your password to send coins) to be part of the next release, and I think that is a big enough feature to bump the next release version to "0.4".
RE: x86-64 client: for the Windows? or for Linux? 32-bit should work find on 64-bit Windows, there's no real reason to do a 64-bit version. For Linux, there should be a bitcoin in bin/64/
RE: bitcoind not forking by default any more: yes, that is intentional, and I forgot to mention it in the release notes. When the mac binary is done I'll update the README. Run bitcoind -daemon (or put daemon=1 in the bitcoin.conf file) and you'll get the old behavior.