Faultless since day 2... Nope. Workable certainly.
It helps to know that a flight plan with a lat/lon sig point, e.g. 2120S15245E, will be really awkward to cancel or amend because some genius decided that the NIS user interface should put spaces in to the lat lon, e.g. "21 20S 152 45E" every time it is re-presented to the user. Try a 30-point Customs run in lat/lons and you will soon lose your sense of humour about it.
Submit the same plan via the 3rd party interface using the decimal lat/lon variant for specifying the point and the notification will be flatly refused with a message that does not gel with the request you sent. Workaround required: use the encoded text as a name like the good old days.
Retrieve a route directory for BN to PH and marvel at the truncated result.
Periodic "Error processing xxx request - Host failure" type messages.
These are the sort of teething problems I expected, not the wholesale smoldering servers result we got.