Probably it is the most waited change in World of Tanks patch 7.3. Although the E-75 can be better in 1v1 situations, the IS-4 is monstrous in World of Tanks. But does the Tier-raise keep the immense fear factor? How can hold on this old piece of steel among much stronger competitors? Does the nature of the IS-4 change in the new environment, and more importantly, does our gameplay have to change? Many questions, but we have several answers on WOT Armory for those.
Update! EU-user Charcharo made a very nice comparative analysis about the IS-4 and other Tier10s. You can find it here on official forums.
Knowledge is power
But first I would make a (not unrelated..) personal remark about the connection between our tests and actually playing. There are tanks they haunt us, tanks we are afraid of in World of Tanks. Then we take one of those to a field test trip, map every bolt and weld on it, the personal bogeyman begins to look less scary. Weakspots we did not believe in before become alive. With our fresh gained confidence we throw ourself in a battle. The once renowned target appears before our crosshairs, we take one breath, armed with the new knowledge we take a concentrated a shot. And guess what, it starts to work! And when the battle is over, we reassess what happened, and suddenly realize our previous little mistakes, those made a difference between a good shot and a bounce in the critical moment. This is how it works from the inside.
Thicker sides than front?
I warn everybody, that I have no personal experience with driving a IS-4, so I always looked at it as a target. But here is something we can all agree on. What made the IS-4 so formidable in the battlefield were the “finger of the death” 130mm S-70 gun (for me, that gun it always looked odd at best in that turret) and the highly resistant side armor. IS-4 could pretty much ignore most things below its tier, unless it were attacked behind. American and german heavy tanks for example never had this luxury.