I just bought a McDermott G208 with a G-core shaft and I totally love it. The hit feels soft and fluid. I like the feedback I get from the hit. It comes with a Tiger Everest tip and I've used those on other cues and love them. It has a little less deflection than a traditional solid shaft, but the difference is not dramatic. Until tonight, I was thinking it is the best cue I've ever owned.
Tonight, I discovered a six inch crack in the shaft. I have no clue how it got there. So I'm calling the store I bought the cue from first thing tomorrow. I've never seen anything like that before on any shaft, ever. I'm hoping it is just some flaw with this one and that they replace it and I never have another issue with their shafts. I played a few practice games with it tonight, after I discovered the crack and it still hits better than any cue I've ever owned. So I really like the g-core shaft. But I'm fairly upset that there is a crack in it. I've only owned the cue for two weeks!
Not sure if this is helpful to you, but I just thought I'd respond since you're looking for comments from people who own either of these shafts.