That depends on what you want to do in Bariloche. It's generally chilly/cold from May to October, and warm from November to March. The Southern Hemisphere summer starts in December and ends in March, when the average daily temperature is 77ºF (25ºC) and at night 50ºF (10ºC). The ski/snowboard season runs from mid-June to early October, and the fishing season goes from November to April. The only "low" seasons are mid-October to early December (spring), or late April to mid-June (fall) - but these seasons have their benefits as well!
Yes. You can safely drink tap water, but most restaurants will serve you bottled water. Patagonia is fortunate to be one of the few regions in the world where you can drink from almost any lake and river since the fresh water reservoir is still pure and far from contaminated. Most water come directly from glaciers, filtered by the mountains before reaching the lakes.
Arriving by air is always faster unless you are coming from someplace other than Buenos Aires or Santiago in Chile. From Buenos Aires it takes approximately 3 hours to travel to Bariloche, with several flights a day from the Jorge Newberry Aeroparque downtown.
The bus ride from Buenos Aires is about 20 hours, and several "classes" are offered including the "coche cama" (full bed), "semi cama" (half bed), and standard. The coche cama is definitely recommended! On board there are movies, a bathroom, and food. There are several competing companies and over 10 departures daily, and there is not much difference between them. Via Bariloche has been recommended as being very consistent, safe, and comfortable.
Yes. Each season the new arrivals are here, and demos of the upcoming season as well. Salomon, Volkl, K2, Burton, Rossignol, and more. You can even find telemark, cross-country, and bici-skis.
The lifts generally open in mid-June and close in early October. Early and late season skiing/snowboarding in hit or miss depending on the year, but the best time to come is in September when the prices are lowest and there is almost plenty of spring snow to fully enjoy the mountain. The high season is usually the last three weeks of July, but is dependent on when the government officially closes schools for "winter holiday". Sometimes this isn't decided until June!