I have not tried the SST bullet. But I hunt with two guys that have used the Hornady factory stuff loaded with the SST for a couple of seasons.
One shoots a 270 Win. and the other uses a 308 Win. Not certain of the bullet weight that they use.
I have seen probably 20-25 deer that these two guys have killed with this bullet. In most cases the entrance wound is indicative of a rather rapidly expanding bullet ..... sort of blown out, with a great deal of tissue damage not far beneath the skin. I had noted that there were not many an with exit wound, but those that had one ... it is fist sized. I helped them skin a few and the wound channel is a mess for sure.
As far as "killing" deer, no doubt that it is suitable for medium game. However, I prefer a less dramatic expanding, deep penetrating bullet such as the venerable (i.e. old technology) Nosler Partition and Sierra Game King. The SST seems to behave more like the Hornady V-Max varmint bullet that the Hornady SP's. It is probably note worthy that I suspect none of these kills was past 120 yards. Our clear shots where we hunt seldom exceed 100 yards.