I know that AHS makes quality boilers, and I believe them when they say they've been engineered specifically for the applications listed. As noted, this is not a wood gasification boiler, so I think it's fair to expect smoke and creosote as part of the deal.
I do have a couple of concerns with multi-fuel boilers in general. First, you're putting all your eggs in one pressure vessel. If you only have one boiler and it springs a leak in the middle of the winter, you don't have very many options. If you have, say, an expensive wood gasifier next to a basic oil or gas boiler, you not only have the backup you need, but it's a separate unit. Either one can be taken out of service at any time for maintenance or replacement, and you don't have to drain your system and move into a motel with the gold fish. A friend of mine had a multi-fuel boiler fail in February in northern New York State, and he had no choice but to buy another one just like it--fast.
Another knock on multi-fuels is that most share a common chimney. That means you could be burning wood, and then switch to oil for some reason. If you don't clean your chimney before switching over, you run the risk of CO contamination due to a plugged-up chimney. For that reason, among others, it's illegal to hook two separate appliances burning different fuels to the same flue, but there's a loophole allowing you to do it with multi-fuel units. It may be legal, but I don't think it's safe, even though I ran one myself for about 9 years. I cleaned the chimney once a week. A wood gasifier combination would be less of a concern because they don't produce creosote.
Finally, in my opinion you always compromise something when you try to combine wood burning with any other fuel. Particularly with non-gasifiers, you simply need different firebox and heat exchanger designs for maximum efficiency. So if it's optimized to burn wood, it's probably not going to shine as a gas or oil burner. Ditto with coal. There are good ways around that--i.e., separate fireboxes/hx arrangements for both fuels--but it's still a compromise. That's fine if the boiler is optimized for wood and you only want the gas or oil as an occasional backup. But it's going to cost you down the road if you decide you'd rather burn oil or gas than wood. I don't believe there were any efficiencies listed on those pages. If there were, I couldnt find them. Saying it's more efficient than other boilers of its type isn't saying much if they don't give you a credible number.
That's kind of like the line about "ASME-certified pressure relief valve." They imply that the boiler is ASME-certified, which it isn't unless you pay extra. Show me a $20 pressure relieve valve that isn't ASME or Warnock Labs certified.
Those are my general thoughts and observations on combination units in general. Other than being aware of AHS's high quality, I can't comment on this particular boiler, having never seen one. The spec sheet doesn't tell the whole story; they never do.
