baking powder

I'm thinking it may be related to your baking powder, but that more liquid would likely not hurt. I've looked at a few scone recipes and here are the ratios I found:

Mark Bittman, How to Cook Everything - 2 C flour, 4 tsp baking powder, 5 Tbsp butter, 3 eggs, 3/4 cup cream.

Zuni Cafe - 3 C flour, 4 tsp baking powder, 1 C butter, 1 egg, 1/2 cup whole milk.

And finally, the definitive Rose Levy Beranbaum's Pie & Pastry Bible - 4 C flour, 2 tsp baking powder, 1 C butter, 2 C heavy cream.

So, there are all sorts of ratios out there, from Bittman's which has lots of liquid to the Zuni which is fairly dry, and I've made the Zuni and the Pie & Pastry Bible scones with great success, so I can vouch for them. Rose's recipe in particular has way less baking powder than the other recipes, but I remember the scones being nice and light and flaky (the cream has a lot do with it, according to Bittman).

Also in the original recipe comments on Smitten Kitchen several people note they have made the scones and liked them.

I'd check the baking powder first to see if there's a problem with it. I know it can expire, or perhaps it's a bad batch. Is Argo the new or the old brand? Argo does seem to be well regarded online - see here: http://www.thefreshloaf.com/node/12997/baking-powder (this is a huge discussion on brands of baking powder, and some of the comments are great too). Definitely people have had bad experiences buying cheaper baking powder with aluminum in it; it has more of that baking powder flavor.

I'd also consider increasing the liquid since the maple syrup will mostly act as a sweetener and 1/4 cup milk seems rather small compared to the other recipes here. I'd consider replacing it with cream and increasing it to at least 1/2 cup.

If your baking powder is one of the ones with aluminum salts (check the ingredients), then it can produce an off, metallic taste, especially when using larger quantities. Rumford is my bp of choice- no aluminum, and I think Argo is well-regarded as well, though it may be a bit more active than many others.

Hi, and thanks for the comments. Actually it is a non-aluminum one. We've had the same experience (bad after-taste) with one batch of biscuits where my husband admitted to not measuring, and probably adding too much.
I've only noticed this since using Argo, and I think I need to be really careful to mix it in well, and use enough liquid so its all activated.
Interesting idea that it might be more active than others. When we don't over-do it, it does give us very light baked goods.