I've been trying to be cautious and not adopt early. I am an Enterprise Gold subscriber. I have app clusters for each of Python/Django, Ruby on Rails, and PHP (mostly WordPress). (edit: All servers are Linux.) I'm now considering taking the plunge. I have hosts to spare, so it's not the logistics of the conversion that I fear. (Unless you have a 5.0 Master + 5.1 Slave horror story to share.) I was reluctant due to a rant by Monty, but I really want a few of the new features. (Especially the additions to the information_schema.) I'm a full time DBA, so I like knowing what is happening to my servers and my data. I work for a news organization, so we don't have the freedom to experience down time like your average LAMP user. It feels like the time for 5.1 has come.
What say you?