In reply to Gaijin:
down quality and fabrics vary, as do features like quality zips, cuff fastenings, fit etc. Hoods are especially tricky to get a good one.
Also bear in mind that the sections of the jacjet have to stop down moving about and there should be no thin spots (stiched through areas eg)
For a thin down jacket, i'd get a quality one as there's less material to do the job so it's got to be good. A big jacket I'd say it was less important, unless you were going on an expedition (i had an M&S one that was great and have a ME one that's too warm for almost everything!
)