I fire a Canon 560 EXII and a Yongnuo 460 II from my 7d using the Canon optical mode, 'ish'. The 460 is a dumb flash.
The 580 EX II is set to be a slave on channel 1. The 460 is set to S1, I have to select the power when I put the flash down. The 7d is then set to master mode/wireless flash. I can choose the settings for the 560.
This means that the 560 is fully controllable from the camera.
The YN 460 will see the pre-flash, and wait (1x the length of the pre-flash I belive, or something like that) and then flash at the same time as the other flashes (whether the 560 or the main camera flashes or not).
i.e. with this setup, I can disable the camera flash from being in the picture, I can disable the 560 flash from being in the picture, but the YN flash will always be in the picture.
I originally bought a really cheap RF trigger (when I had my 400d, which couldn't do optical), it fell apart quite quickly. If you get an RF trigger, go for a decent one (not a no-name brand, YN should be OK I would think).
However, I am now at the stage where I wish I could do more. The YN 460 is not TTL, and I find the lack of any RF trigger a little anoying. The recylce times on the flashes are great, but sometimes in a bright room it is difficult to get them to trigger.
The 'problem' with adding an RF trigger now, is that I would loose the ability to use the 7d onboard flash, which is quite useful, if just for a 'fill in' light to get rid of some of the bags under the eyes sometimes.