Caveat: I haven't played in about a year, so this might be totally off. But I think these are all fantastic barriers. They certainly were when I was still playing (when both paperclip and corroder were in play) so they're probably all still worth at least thinking about:
Special mention goes to Vanilla - it's a fantastic piece of gearcheck ice. Forcing them to go spend 4 to get in, when it costs you zero, is always a good tradeoff.
Also, Meru Mati is crazy-efficient at guarding HQ. Not great otherwise, but often worth a slot or two in the deck.
As for the rest - they're just big, annoying pieces of ice. They will generally cost you X to rez, and cost the runner X-1 to get past. Which means that the first time they go through, you'll take a slight loss, but every time after that, they will be fairly taxing.
Because they're ETR subs, they're going to be at their best if you force the runner to actually break them though. Put them on HQ and R&D, or in a server that you put things that might be agendas, but aren't always. They really are kind of taxing, and unlike some ice, there is no real negotiating with them. The runner can't let just some of the subs fire, to blunt the cost, or make a desperate run. They either pay up, or stay out, and you can abuse that economically.
My $0.02 at least. Again though, haven't played in quite a while, so it's possible that something has changed to make this far less effective in practice than it is in my head. :D