In "Does running an alternative full node implementation benefit the Bitcoin network?", I asked about running an alternative full node implementation for the benefit of the Bitcoin network.

What is the current status of different alternative full node implementations with regard to

maturity (alpha/beta/stable)

performance

compatibility tests

code review

suitability for different purposes: experimentation merchants as a wallet as a lightweight wallet back-end solely for the benefit of the network?



Update: Moved the list of implementations into an answer.