I made an OF with Gentleman Jack this very weekend, it was very nice. I used Bowmore No 1 for OF a while ago, but only to use it up. As you say they give a different drink and it was better than drowning it in ginger, this being Plan B for the rubbing alcohol variants.I probably use bourbon (or other US whiskies) about half the time - Gentleman Jack and 1792 are both great for old fashioneds. The ones with malt are quite different though, as does the type of malt used. The Bowmore 12 is another I mostly use for old fashioneds as well.