Generally, the safest way is to stick with the default settings provided by the configure script.
Features marked as EXPERIMENTAL should normally not be enabled in a production environment unless you exactly know what you are doing and are aware of possible consequences.
To figure out which configuration options were set execute a phpinfo();. Scroll down to the APC section and check what Locking type tells you. By default it is something like thread / mutex locks and if it doesn't mention the spin locks, they are most likely not enabled.
Note that this is from memory - cannot verify this on a live server at the moment since I prefer eAccelerator over APC.