Kalikiana, you can connect to the U3 to your hotel from the OBB, but I think you have to purchase a separate ticket for the U3 (2 Euros per person) at Wien Mitte. Your hotel looks closer to the Rochusgasse station off the U3 rather than Wien Mitte (Landstrasse) station from your arrival at Westbahnhof, as well. The transition from OBB to U3 is easy and well-signed.

You'll need to price-check the value of the Vienna Card, depending on what you want to see. You'll need public transportation for seeing the major sights from your hotel location. The card is good for 72 hours, and offers discounts for various sights as well as unlimited travel on public transportation.

Thank you fourfortravel! Yeah, I was trying to think if it'd be worth it to buy the Vienna Card. Are most trips into the center 2 Euros? In that case, if we made 10 trips (5 round trips) in our 3 days there, it'd be worth it to spend the 20 Euros on the VC for the travel alone, right? Or am I missing something...Not saying we'd definitely take 2 round trips from our hotel each day, but I wouldn't think it'd be out of the question?

The full price ticket is 2Euros at the machine in the station, and 2.20Euros if purchased on the tram. You can also purchase a 72 hour transit ticket for 14.50Euros at the stations, good for unlimited travel.

Ooh, ok. That may be a better option then, thank you! Last question: after we purchase the ticket, I know we have to validate/punch it in one of the machines. Do we have to do that before every trip or just once before the first time we use it?

The ticket needs to be validated only when you first use it; after that you are fine for the remainder of your travel. Arriving at Wien Mitte you can purchase and validate your long term ticket if that works best. Otherwise, just purchase a single fare to your hotel, and buy a timed pass the following day. As an FYI, Vienna public transportation is an honor system, and fines are hefty if you are caught without a valid ticket.