Seems to be very useful for PK lookups, but I haven't seen much information regarding this. What's the pros and cons of the handler syntax vs. ordinary SQL select for simple key-value queries? How does it compare (performance- and consistence-wise) to HandlerSocket?
This was a weird question. I say was because I addressed this in the past
Jun 17, 2011: What are your use-cases for HandlerSocket?
Aug 12, 2011: Which DBMS is good for super-fast reads and a simple data structure?
HANDLER syntax is kind of handy if you want to read table data from table while bypassing locking and transactional isolation levels (Yes, this means you should be able to bypass InnoDB's MVCC protocols).