and it looks like it basically just gets you discouted tickets where the pass is accepted.
Not really. There are a large number of trains and journeys which you can travel on completely free of charge with your pass.
HOWEVER, there are also a large number (normally of top end trains) that you then have to pay supplements to use. Certain countries (Spaain, for example) it is compulsary to have a reservation except on the most local of trains, and these you again have to pay for. For night travel, any kind of accomodation above a basic seat, you also have to pay extra for. Sadly, increasingly in much of western Europe these days, even seated accom on night trains requires a reservation or supplement.
On most of these trains, the supplement costs are small, but they can and do add up fairly quickly, especially over time.
For 3-4months, its likely that you will be making more shorter journeys than longer ones, and thus point to point may well be of better value to you. This is especially true if you can book some ahead of time, and take advantage of local discounts/special offers.
However, depending on your schedule it might still make sense to buy a pass for part of your trip - Maybe for one month - especially if you are planning on travelling allot/longer distances etc in that time. It all comes down to your itinerary as to whether it will work out. But I seriously doubt that passes for the full 4 months will be value for money.