I have the G500s and I love it for casual use. For speedrunning I don’t like it because I feel I lose a lot of control with it. But I do believe that freescrolling could be learned so it provides at least equal control and not really have any disadvantages. It becomes hard to time jumps with freescrolling as it doesn’t really do inputs in even intervals, at least not if you’re just flicking your finger and waiting for it to slow down (unless doing mindless spamming, most of the time I’d say you should have your finger on the mwheel).
For HL1 freescrolling works very well with higher fps values and for 100 fps it is quite a bit harder to use but should provide a big advantage if you master it.
For hl2/portal I believe it’s much harder to use but haven’t tried it a lot. Once again, it depends on how used you are to using it. For me it would probably help for my first abh but after that it would be horrible.
Even though it’s banned in HL1 I still think you should experiment with it and if you like it, you should keep it. Maybe at some point there will be a new vote about freescrolling as it becomes more common.