If it's worth it depends on where you're going and which trains you'll use. Usually long-distance and high-speed trains have a real first class with more room etc. Regional and local trains may not always have first class or or only a first class "in name” that doesn't offer much extra.

Optional seat reservations are usually the same price as without a pass. Mandatory seat reservations  are usually include with a normal ticket, so these are extra if you have a pass.

@rvdborgt I will travel for 3 month. Most time spend in Spain, Italy, Germany and Scandinavia.

“Optional seat reservations are usually the same price as without a pass. Mandatory seat reservations  are usually include with a normal ticket, so these are extra if you have a pass.” 

I don’t quit understand. Now I’m wondering what exactly am I paying for when buying the 1st Class Global Pass. 

First class should have more space for passengers (in long distance trains anyway). That's mainly what you get with 1st class.

@rvdborgt  Okay so without interrail pass I would pay more because the reservation + the perks of 1st class and with a interrail pass, I only pay for the reservation since I payed extra on the interrail pass.

Depends and totally varies with country. NOte that f.e. in Scandinavia nearly all local/regional trains are only standard=2nd cl. In East-EUR often same and hardly any benefits.

THE very best country to opulantly use 1st cl is the UK: on IC-trains you get free food/drinks, much more space and you have also access to many nice lounges-also with fd&drk in most major stations.

IN DK you also get free cf/T/OJ in 1st/ICtrains of DSB.

In Austria there are nice lounges for 1st cl in all major stations. In DE they have these too, but YOU with just a pass cannot enter!!

Overnight trains-if they even have seats, generally NO 1st cl-then you must book sleeper. It is NOT true that you always must REServe for 1st-again this really depends per country.

In some countries use of 1st is hardly enforced and each&sundry sits there. In others its mostly the tipical govmt workers on job-trips who will sniff at those stinky USA-EUrail users (in the past these people could only buy 1st cl. passes and hence the general image)

If you really worry too much about money, then skip it.

First class pass is NOT worth it! The problem with the eurail system is that you can buy a first class global pass but then you also have to buy first class seat reservations for each train to assure you even have a seat in first class and because they are first class reservations they typically cost more as well so you’re paying more just to end up paying more again for reservations. Another weird thing is that anyone can buy first class seat reservations so there isn’t even a guarantee that there will be any an available to purchase even tho you have the first class pass. Also, the difference between first class and second class is really just wifi, seats that slightly go back, and the seats are the slightest bit bigger. Sometimes they give you free water too.