Why I cannot let EXPLAIN update statements? I can imagine that it's actually more important to explain SELECT statements, but I wonder why there's no possibility to use EXPLAIN on UPDATEs/INSERTs.  I may use a WHERE-statement in an UPDATE where indexes are being used (I guess?), it should be possible to see if they are actually used.  Additionally, in the case of using a SELECT-statement inside an UPDATE, I also cannot use explain for this part without getting a syntax error.
Did I misunderstand something about the processes on UPDATEs and INSERTs?  How else can I else debug those statements?
MySQL currently doesn't support this (unlike nearly all other DBMS). 

I think this will be in 5.6 but I'm not entirely sure.

I don't think there is any workaround for that (except upgrading to a DBMS that does support this)