Never used, but some comments. The Reefmania skimmer looks very nicely built. I like the fact you can unbolt the neck from the body to clean the body (although I have to admit I've never bothered cleaning any of my skimmer bodies). And I've always liked grey gate valves

The down-sides I see are:
1) the neck isn't tapered like Euroreef, Deltec, Bubble King, etc. The tapered neck, IMO, really helps with foam formation.
2) Sedras (and Oceanrunners) are good, but Eheims are better. Costs a lot more though.
3) The intake and outlet plumbing planning don't like very thought-out. I'd be afraid a lot of bubbles escape out of the skimmer back into the sump.
At its price, I think it's a worthy contender to Euroreefs and Deltecs. Personally, I wouldn't say the Reefmania products (any of their products, not just skimmers) offered anything innovative or of very high value to make me move away from the proven designs. If they were priced cheaper, I'd certainly consider one.