Overnight train from Vienna to Bregenz (per person): couchette in 6-bunk compartment 22, couchette in 4-bunk compartment 30, bed in 3-bed sleeper 50, bed in 2-bed sleeper 65 to 79.
Reservation fees are generally the same whatever type of rail pass you have.
It is definitely worth buying if you're planning an extensive tour with a Eurail pass - having your own comprehensive timetable puts you in control of your own trip, and will save you hours in queues for station information desks or struggling with station timetables which show only the most basic information. he European Rail Map of Europe is easily the best and most comprehensive map of train routes all over Europe.
High speed and scenic routes are highlighted - well worth buying to go with your rail pass! There are other maps & even two good European Rail Atlases, see here.
**** You can buy a 15 Belgrade Special fare any day, any departure, online at see the advice here.
The countries participating in the Eurail pass scheme are Austria, Belgium, Croatia, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Romania, Slovenia, Spain, Sweden, Switzerland, Turkey (which joined in 2013), Poland, Bosnia, Serbia & Montenegro (these last 4 joined in 2015). Eurail does not cover the UK, Albania, Macedonia, Ukraine, Russia, Moldova, Lithuania, Latvia or Estonia.