I've encountered lag and crashes so far playing, and ive read about disappearing party members. But from what i read its only when you dismiss them from the main party. Normally they go to the ranger canteen. Where you can pick them back up if you want. Obviously if you have the bug. They wont be there waiting to be picked up. Mission objectives are slightly confusing, and its annoying not to have markers on the map on where exactly to go. But its a older game, and doesn't hold your hand like we're accustomed to. I would pick it up however. Just save often.