High-efficiency boiler and water heater replacement

I've been considering replacing my hot water heater with a tankless system, such as those made by Rinnai or Noritz, as many people have. But now I've come across a unit that claims to provide both hydronic heating as well as domestic hot water. It's the Laars Mascot HT 330. Some info on it can be found here:

http://www.laars.com/reshydronicboilers.htm

Has anybody installed an HT 330 or something similar to replace both their hot water heating and radiant system boiler? It's quite a bit more expensive than a tankless system devoted to domestic hot water, but it's comparable to the cost of a boiler providing only heating. The domestic hot water heating function therefore is basically "free" and considering the very high efficiency of the unit and the potential space saving, is this a good solution?

Thanks!

Dan