I checked it yesterday and the Enom domain registration command was not realtime during the drop as far as I can tell.
It still showed "not available" while the domain was already available to register.
Perhaps this could have been due to caching as I had used a proxy server but to me it seems it does not update fast enough to be useful. You could beat it handregging.
I think I had smiliar problems with Gandi and Godaddy was horribly slow during the drop when I checked it.
As far as I can tell these APIs are worthless.
Dynadot and Namesilo seem to work well though.