Standard Resilient Channel
Resilient channel really is not that bad of a product to use in walls. Realistically you can bring up the rating of a wall by a good 10 STC points with resilient channel. Most gains are in the mid to high frequency range with very little improvement in isolating low frequencies. However, the STC increase might just be enough for you if you need to block basic sound transfer such as people talking in the next room or light TV noise. Resilient channel can be difficult to install properly without experience and prior knowledge of the common pitfalls of resilient channel.
The performance increases achieved in walls do not translate well into ceilings. Ceilings are more difficult to isolate than walls because of the mass and rigidity of the structure. Airborne noise isolation will improve slightly from the addition of resilient channel while footfall impact noise isolation will not be affected.
A common mistake with resilient channel is the retrofit installation over existing drywall. This causes all sorts of issues with resonance (read Triple Leaf Effect) and the end result is no gain from using resilient channel. Resilient channel can increase performance in a wall by 10 STC points, but if installed over drywall, creating a triple leaf, then the performance will be brought down to a measly 1-2 point gain. Adding resilient channel to a ceiling will increase the rating by 5 STC points so installing over drywall will actually leave you with a rating lower than what you started with.
You can do pretty well using resilient channel in walls as long as you install it properly. Take your time installing to make sure you do not short out your installation. Installing resilient channel in your ceiling will not provide great results and no real improvement for footfall impact noise. Resilient channel is a decent solution for sound isolation in walls, but there are better products out there with similar cost and more fool proof installations.
Resilient Channel With Foam or Rubber Attached
Some project specs call for resilient channel with a thin foam installed on the channel and/or between the channel and framing. Some manufacturers have put together a resilient channel with foam or rubber pre-attached along with a foam or rubber base to install between the channel and the framing. This seems like a great idea, but in the end all you will end up with is the performance of basic resilient channel. No true sound test comparison would show otherwise. The resilience of the resilient channel still has not changed as it is still fixed at every joist or stud. Unlike resilient sound clips that have a connection only every 4′. A span that greatly improves resilience because of the minimal connections keeping the channel from flexing (isolating vibrations).
Do not bother with these types of products. Go ahead and use resilient channel, but do not think that using foam on the channel will actually give you a jump in performance beyond an inaudible 1 STC point gain. The reason why these types of products exist on the market is because it is nearly impossible to make a profit off selling resilient channel unless you are a local distributor. To compete online, companies had to come up with a way to alter the resilient channel to make it more appealing than basic resilient channel. Perceived value goes way up, actual value is unchanged.