I'm planning to visit central Europe this summer - probably July/August, and most of my time will be spent in Austria. Although I've seen plenty of Germany and some of Switzerland in recent vacations (I live in the UK), I've not seen much of Austria - in fact, just the line from Innsbruck to Garmisch. and Salzburg for an evening before catching a night train, which have both whetted my appetite. I'll be travelling by train, including Eurostar to and from Brussels, and probably using night trains to get between Cologne and start/end destinations - Vienna for one and maybe Innsbruck or Zurich for the other. I'll have an Interrail global pass for all my journeys. I tend to stay in hostels as I travel alone and don't mind dorms.
So, I'm thinking something like this:
Vienna, 4 days, including a day trip to Bratislava, and another to Melk & Krems
Hallstatt, 1 day, possibly between Vienna and Salzburg, or 1 night if worth it?
Salzburg, 2-3 days, to see the city & possible SOM tour, one day to see Berchtesgaden - something I planned to do last year but gave it a miss due to poor weather.
Innsbruck/Hall in Tirol - 2 nights maybe, if worthwhile - any other Tirolean places more attractive yet accessible? I understand Innsbruck is nothing special. After the above two cities I'll be looking for something more mountainous/rural.
Southern Tirol/Dolomites - Having watched 'Alps of Austria and Italy' this region looks promising. Kastelruth perhaps.
Other places I've considered are Germany's Black Forest & Switzerland's Appenzell, but can't do everything!
So any advice on places to see or miss, places to stay, would be very welcome. What are Austria's HI hostels like?