I really like SemanticMerge, it makes total sense, although the diff experience is unlike other diff tools in terms of immediacy. But I think it will be another great tool to add to the arsenal when you need to pull out the big guns on crazy diffs.
Absolutely. I had it installed for some time and mostly thought "this is really neat but I could live without it." And then there was a monster merge with significant conflicts all over the place. I don't think it would have been otherwise possible to pull it off with as little damage as there was if not for this tool.
I really like SemanticMerge, in its current shape it is litte more than a fancy proof of concept.
Its biggest limitation on real projects is that it works on a single-file level, while all the interesting stuff happens on patch level. You may browse their forums to get an idea of what else is missing.
That said, I wish all the best to Codice and I really hope that they continue to invest in this tool.