Samuel Adams is now regularly available at Wellcome, or at least some Wellcomes. So in my opinion that's a significant step up on what's normally available in most supermarkets here.
Danshui Carrefour's selection is currently very good: IPA and amber ale (and maybe blonde ale?) from Washington State's Scuttlebutt brewing (450NT for a six-pack I believe); and a bunch of different kinds from Mexico's Day of the Dead beer, currently on special for 55NT each (regular 65NT): Hefeweizen, porter, amber ale, blonde ale, pale ale, IPA I think. I have no idea what the quality is yet, it being still before noon with a lot of final term paper marking to do today, but the packaging is really cool. Plus, I believe until June 23, there's a sale on lots of other beer too. I think they're also selling stuff from a local microbrewery too - North Taiwan Brewery, or something like that? - which is a great omen for the future. However, the packaging is all in Chinese, and that fancy looking Mexican stuff was cheaper, and I couldn't carry anymore, so I didn't investigate much. Yet.