This is a very taxing card for the runner indeed. If the subroutine is not broken then they would suffer a major tempo hit, potentially losing an expensive card back to hand.
It also offers NBN a relatively cheap, efficient and taxing piece of ice to add to its repertoire. Rush and kill decks both would benefit from its inclusion.
However, it is a weak early game piece of ice because the runner could be running without any cards in play, thereby nullifying its impact. So if it is installed early, do not rez it until its subroutine will do some major tempo damage.
Regarding the R&D access option, consider the cost/benefit of activating the ice in relation to the current credit differential between yourself and the runner. It would cost you 3 credits to activate it, but the cost to the runner could be much more than this. However, the rez cost is just 4 credits once on the table, so many times you may opt not to activate it from R&D.
If you can rez this ice at a point where the runner has a lot of cards installed, and does not have a cheap way of breaking the subroutine, then this card is sure to reap a solid dividend.
As a Prepaid VoicePAD Kate "Mac" McCaffrey: Digital Tinker runner, I really find this ice to be a major problem these days!