I have for some 15 years, used a FlightLink GStick II with centering springs. It was expensive when I bought it to install in the helicopter sim I was building at the time, but there's more to flying satisfaction than money. For years, it performed well (as did the cockpit I built, in fact I still use it), but like all mechanical things it began to give me problems so I just recently acquired a new FlightLink GStick III to replace it. This time I ordered it without centering springs and after a week or so of getting used to it, I'm glad I did. It is a much more realistic feel since not matter where you position the stick, the resistance is the same. I have yet to use any of my normal tricks, or any mfg force trim while flying. From the stock Bell 206 to the Dodosim 206 to the Milviz 407, they all fly without any centering problems.
Also, the feel of the stick is much more like a real helicopter to me. Although my experience with real helicopters is limited to the R-22 and the Bell 206, both of which have different control systems (one mechanical and one hydraulic), this stick does an excellent job of mimicking both. Although to me, given the fact that it does have some resistance to moving, it feels much more like the Bell than the Robinson. Another thing is that no matter what, you can takes your hand off the stick and it'll stay where it is.
Although, it'll still take some getting used to, I'm finding my flying is much more enjoyable than before. As I continue to get used to it, I'm finding that the money I spent was well worth it to me and that I really like this stick a lot.