I have both. They are different shoes for different uses. The Boston is firmer, more built. I'd call it a lightweight neutral trainer/racer with fairly minimal support.
The Feather is an ultra-lightweight neutral racer with absolute minimal support.
You will probably find the Boston very similar to the lunarglide -- it's a good all-rounder, relatively light and responsive. It's also well made, so you'll get good use out of it. I've not put many miles in the Boston 3's (just got them on Monday) but I had several Boston 2's that were great through 500-600 miles, after which they started to feel a bit dead under the forefoot (seems to happen to me regardless of shoe). Cosmetically, however, they were perfect. I really like the Boston range as a marathon shoe, and have even seen some 2:20 marathoners wearing them.
The Feather on the other hand is really designed with ultra-lightweight in mind and the upper is very thin and light, and the sole a very basic construction. They feel really light and more bouncy than the Boston. I'm going to keep them on the side for most winter training but will use them for some workouts and maybe as my next marathon shoe. But I don't think they'll go much further than 300-400 miles.
What is interesting is that in some shops and some Adidas sites the feather is being marketed as a "teen" shoe.... I gather this means that a 200lb heel striker shouldn't buy them and expect them to last :)
In summary: Boston... a great neutral trainer; Feather... a great tempo/race shoe (as proved by Mutai in NYC).