Those who run full node can check out BTCDrak’s own RC of Bitcoin Core 0.12 with addrindex (which is required for Counterparty Server).
I tested Win32 and it seems to run much faster than v0.11.2. Having said that, there are also some 0.12 bugs (see Bitcoin Core issues on Github).
But because there’s nothing to install (if you use BTCDrak’s prebuild binaries), it’s easy to test without uninstalling existing Bitcoin Core (0.11, for example) - you can simply run 0.12 from any directory and point it to your existing configuration file.
If your current blockchain doesn’t have addrindex, then of course a reindexing would be required, but in case you go back to 0.11 (or non-addrindex), you wouldn’t have to re-download the blockchain.