Definitely a major, major impact - I'm not sure of the right word ('easier' doesn't feel right somehow as it's not), but I've had too many recent experiences for it not to be the case. Things like - Three Forts (first time I've run an evenly paced marathon, and strongest finish), Brighton (first sub 4 for 4 years despite horrid last 10k), SDW Relay - ran all three legs at the same average pace (8 min miles - never remotely approached that during that event) and SD marathon - 30 minute course PB. I'm actually running less (typically twice a week outdoors and two treadmill sessions - 'less is more', focusing on quality and not junk miles). The 'extra' 8m run last night didn't feel remotely difficult - even though it started with a run from Clayton Village up to the Windmills (you know how steep that is - I ran all the way up)
Running doesn't cause residual pain any more - it's truly startling. Biggest example of this was doing 45m bike ride the morning after the SD marathon and not feeling remotely stiff
I just need to start to rationalise in my head now how I approach things going forward. At the moment I'm happily plodding along and enjoying it, with no real objectives other than ticking over and doing the events I've planned in reasonable shape and not getting injured, and using every run to focus on getting technique right (I still have work to do - after 18 months). At the end of the year (after New York) assuming things are still going well I might knuckle down and see if I can train for a marathon PB (but I'm not hugely enthusiastic about it - an course PB on SD was to me a bigger thrill), and then I'm contemplating moving up (but time is an issue for me)
Sorry, long and boring post I suspect. If it's not Chi running I don't know what it is - yes, a bit of weight loss has helped, but that doesn't explain the lack of injury (nothing for almost a year - unheard of for me as you all know), the lack of post-run stiffness, curing of the cramping problem and most of all the feeling of 'floating' or coasting when I get the technique right - which is happening more and more often, and for longer spells. It's truly surreal after years of struggling, but I can see why some people wouldn't get it - it takes many, many months of work.
Have you booked your course yet ?