The CFL & LED are tricky because there are so many variations in manufacturer, quality dim-ability, etc..
Lutron has put together a pretty good tool to help though. Check out:http://www.lutron.com/Service-Support/Technical/Design-SelectionTools/Pages/LEDDimmerMatrix.aspx
If you visit that page simply select the Lutron Control type you are planning on using and it will populate a list of tested fixtures and lamps. If you can find the LED product you are trying to use it will have a link to what they call a 'Report Card' of how well it performed, min&max number of fixtures or wattage's, etc..
In most cases though their RRD-6NA ("adaptive") Dimmer is the best solution. There are some counter intuitive points to note though. For example the Cree CR6 using the 1000w Neutral dimmer (RRD-10ND) can only handle 5 CR6 units (only 55watts) however the RRD-6NA (600watt) can handle 6 CR6's with slightly more range also.
Lutron is telling us the high inrush of these LED drivers is the reason you couldn't use more than 5, even on a thousand watt dimmer. (Use of interfaces will allow more fixtures and may necessitate an Fluorescent Dimmer or QS to control on an R2 system.)
The "report card" also shows other non-system dimmers such as the Diva, Maestro & Skylark. So it is a useful tool regardless of RR2
For CFL, you should still use an appropriate dimming ballast and corresponding dimmer like the F6AN for best results. Though the adaptive dimmer may work on certain 2-wire dimmable CFL lamps and ballasts. For the price of a well functioning dimmable CFL system, you may as well consider the LED version, as they are coming to near the same price or better.
about the LED Ad nauseam earlier this year, if you would like to read more...