Research treaties, if acquired at the right time, can really help your empire out. In the early game, get research treaties from as many empires as possible. They're usually in a big financial hole, and will part with these for peanuts. Later, when they're big empires, you get significant research boost. I've had games where I'd set my research slider to zero, because my research was only 30-40% of the total research (the rest coming from the other empires), and I really needed the money elsewhere.
Where this really shines is with minor empires. Unlike the AI, these actually are doing significant research, thus you get a big boost from them. In a recent game, I had eight of these empires in the map, four or so nearby. Each was giving me 20+ research points per turn. My empire at the time, with a 40% expediture, was only able to generate about 30 research points (this was early in the game). Since I couldn't compete, I diverted that 40% expenditure to military production to build more colony ships faster. This let me get a big leg-up on the other empires.
Once you get big, the benefit is much smaller. But getting those crucial techs early on during the planet-grabbing phase can mean the difference between being small and bankrupt with unhappy citizens, and being big, with cash rolling in, and happier citizens. Those early techs are cheap, thus that extra research from treaties can make a huge difference.