I use the H751 cue as my main playing cue with an I2 shaft.
I like everything about it except for the fact that the weights seem to come loose every month or so and I have to take the rod out and tighten the allen screws on the weights. When they come loose you can feel the vibrations in the cue.
Having said that the last time I tightened them I gave them a good crank (a tad more than I was comfortable with) and they have not come loose since then (6 weeks now). I seriously considered using clear nail polish or loctite on the threads, however I was worried about creating problems down the road if I ever wanted to get the screws out.
If you need to buy more weights they are fairly expensive as well and they don't have a kit that you can buy. I looked into changing my 1/2 ounce weight to 1 once weight and it was over 30 bucks with shipping.
The reason I got this cue is so that I can experiment with different shafts and be able to adjust the balance point so the shafts all have the same feel.