I have no experience with it, but I'll give my impressions anyway.

First, if it was a gift, you can't beat the price! I don't see it being worth much more than a piece of sheet plastic for the task, but the price you paid (free) is right.

Be careful about filling the reservoir with water. I think too much moisture could lead to rot instead of root.

It's hard to tell how it grips the tree from the pictures in the link. With a piece of plastic, you aren't limited to a certain size. The Rooter Pot appears to have a limited range of acceptable stem size.

If I was given a set of these, I'd try them, but I doubt I'd fork out the money to pay for them otherwise.

The purported advantage of this pot compared to the traditional method, is the reservoir of water intended to keep the moss damp with out your constant attention. I have used these and find you must be careful to chose a branch VERY upright so water can be added at the top. You should also wrap the outside with aluminum foil to keep out light and keep the roots from heating due to the sun. For me I think the old way is easier and if sealed properly and the moss is prepared carefully adding water will not be necessary. Mine were not a gift either. Al

I have used this type of propagational device a few times with success most times. Like calistoga says, you must keep the pot very upright. I have resorted to tying branches to rebar rod to keep them upright. That's probably the hardest part of the process! I find that propagating cuttings directly in seed trays with with a plastic cover is a whole lot faster and I can take a lot more cuttings.

I have used it and had some success but had as many failures because of the root breakage if not left long enough on mother tree to have a good mass of roots as shown in the picture. In many cases I will have good roots but good part of it will be severed and left in the pot.
I then stopped using these and started using burlape or other bio-degradable cloth or other sheets around the rooting media so I just cut the rooted branch and pot it without disturbing the root by opening the roots bundle.

Thanks for your reviews. If I chose to propogate some shrubs or trees using the same idea that the rooter pot uses but using other materials how do I go about it? what do I use and do i have to check it regularly etc.

Most propagation books will cover this in detail. I like the reference from the book Plant Propagation, by Philip McMillan Browse published by the Royal Horticultural Society in paperback as part of the Practical Gardener Series. The handling of the moss and wrapping and sealing are very detailed and crucial to the success of this method. Al