I can't tell you if it is more temp stable than IMR 4350, but when I had some for my 6.5x47 I was getting faster MV than I am getting with IMR 4350. At least I have good accuracy with IMR 4350. I will know more about temp stability of IMR 4350 as summer progresses. I am in south AL and will be shooting in near 100° F weather before the summer is over. The upside is that I don't think I can get enough IMR 4350 in the case to be dangerous. Will just have to watch for pressure signs and chronograph some rounds on a regular basis as the temp increases.
But, if what I was told last weekend is true then some H4350 may be on my horizon.