Upload & Sell: Off
Ok I won't be so dismissive . But I will also agree that a proper cf card is a better option. Decent moderately fast ones are pretty cheap. And unless you are going to hammer out the gb's on every session a Couple of 32gig cards would be more than enough for most users.
But I will say that I am using one in my 7D most of the time.
I'm using This one but my reasons may not be any good to you.
Here' my reasons and experiences.
My reason is that since the fw upgrade of the 7D it has made the ability to shoot raw&jpeg together much better. And my iPad (that I use to view and cull my images , and also just to show others) loves jpegs much more than raw. Raw is much slower to upload to the iPad, and also the cable to tha camera option is slower than the SD reader part of the cam connection kit.
So if I just shot raw I would have very slow upload (trust me a while back I discovered what slow was when trying to save a few hundred raw files to the iPad between bike races. It was so slow as to not be worth it. If i had waited until it was finished I would have had a dead battery and missed the next race).anyway. And if I shoot raw+jpeg it uploads BOTH files and I have no way of separating them .
So my workaround is to shoot to SD in the adapter. In fact I'm shooting to a Samsung MICRO SD class 10 . I'm shooting RAW+jpeg . I can then insert that micro SD into my phone and very quickly cut/paste the raw files out of the dcim folder (the iPad only looks for this folder) . I then upload the jpegs to my iPad . And I'm happy.
But as with most thinhpgs there are some drawbacks.
Speeds are slower. But they are not prohibitively slower most of the time (that increased buffer helps).
I did a speed test and found that the micro SD class 10 was about twice as slow as my transcend 400x CF .But it was faster than my transcend 133x CF by a little bit. An old class 4 micro SD was snail slow. So SD card speed does have an effect. . But then I also tried out an old Sandisk Ultra 2 (not one of the newer ultra with the speed on) . This was only just quicker than the very slow class4 SD.
Like I said I'm doing it for a reason. If I don't need the iPad then I just use my CF cards . I would not go down the adapter route for just the reason of having lots of SD cards .
Hope that helps.
Oh by the way I know others have looked into the adapters when they don't want to stress weak pins in their body (an expensive fix if needed) but adapters that take 'normal' size cards have to be removed from the body anyway, as the SD inserts in the side. (Not enough room otherwise) but there are micro SD adapters that don't need to be removed from the body. But from what I gather these are really slow.