My story and my 2 cents...
Rafed's post came at a very opportune time for me. I had planned on grafting most of the cuttings I had received. Also grafting was going to become my preferred method of dealing with cuttings. After I had split the long/branched ones, there were 22 varieties/88 cuttings. I was out in the field in late January and noticed many of the limbs I had planned on grafting onto were damaged by the cold, and I had a problem. I used the last of the sphagnum moss last year, so I was faced with buying another bail of it to root cuttings in. Instead of moss (and Rockwool which I have used before), I purchased one of these kits.
I set 50 cutting into the tray on 02.04.2013. The cuttings ranged in diameter from 1/8th" D to over 1/2" D and from about 3" long to over 8" long. I had 30 cuttings (15 varieties X 2 of about the same size) which I mirrored on either side of the tray. One side I used the rooting hormone that came with the kit, the other side I did not. The other 20 slots I used the rooting hormone except on 4 which I received already dipped. Here is what it looked like when I was done.

Instead of buying the humidity dome, I used a clear 18 gallon tote as my "greenhouse" then set the tote near a south facing window. The position of the tote in the window gives it sun in the morning through about 1pm to warm up the interior, then light from the sky until about 6 as the sun starts going down. This was my M.O. with SM in zip top bags. Every other day, I "water" the cubes with a spray bottle with the nozzle set on a fine mist. I spray 10 times above the cuttings and 2-3 times into the top (the tote is upside down so the tray sits on the lid). I did this until the 02.12 when I started traveling, then my niece took over for me, but wasn't as diligent as I was about watering.
I returned from my trip last Thursday (02.21) and checked my cuttings. Four had rooted. Three of the four are 'Lattarola' (2 with hormone / 1 without) which had rooted profusely. Every night since then, when I checked I have found 4 more cuttings with roots. Here is the current state (taken 02.25):

The 'Votato' in front (and a few others you can see) have some mold issues, but I do not blame that on the Root Riot or my system. It may become a subject for a new thread. Now my observations / thoughts / responses to things mentioned above:
- Thus far, my results have been encouraging enough for me to consider buying another tray and not worrying about grafting the remaining cuttings.
- I do not think this is a replacement for anything other than putting cuttings in a baggie with sphagnum moss for root development. As such, the cubes are not too small.
- There is a slight bit of inconsistency in the cubes as far as moisture retention. I've had been two (out of the 50) that I have had to mist with the sprayer away from the rest of the tray. Someone mentioned in one of the threads how nicely the color of the cube changes as it begins to dry out.
- To HungryJack's comment: I am not sure I would wait for a system "specifically designed" for anything. I would assume due to it's specialized nature it would be significant more costly. For 20 bucks, many of us have achieved similar results in different parts of the country. It seems as more of us are trying this system and any problems will begin to flush out. However (with my n=1) I haven't found this system to be wanting in any way.
BTW - so far 11/16 were dipped in the Clonex and 2/16 were not. The other 3/16 are in that group of 4 cuttings I received already dipped in root hormone (I'm not sure which one).