I spent 6 weeks in the Czech Republic and it was GREAT!!! I went to Vienna to spend 3 days, before I flew out and had problems.
1) I arrived at noon on Saturday. Everything closes at noon on Saturday.
2) I came to Vienna for a weekend. All of the locals leave town on the weekend.
3) Many restaurants, museums and cultural treasures were closed.
4) I was in town on Monday, but it was a Saint's day and everything was still closed. I flew out on Tuesday morning.
RECOMMENDATIONS
1) Go to Vienna during the week.
2) Look ahead and make sure there are no official holidays.
3) Bring plenty of money and do not stay long. It is quite expensive.