LWTs were added for a very simple reason: stronger isolation where the performance trade-off makes sense. Nothing to do with the GP comment.

Until recently they were indeed slow over the WAN, and they remain slow under heavy contention. They are now faster than peer features for WAN reads.

However, the claim that they have many bugs needs to be backed up. I just finished overhauling Paxos in Cassandra and it is now one of the most thoroughly tested distributed consensus implementations around.