Just a bunch of impressions from the 8.5 test on the vehicles at hand. I'll be skipping the lowbies, I'll get straight to the good stuff: Indienpanzer, Leo prototyp A and Leopard I.

The Indienpanzer plays a lot like Panther or Panther II. The 90mm gun has a long aim time (2,9s), but it is reasonably accurate and fires fast enough. Its performance is comparable to the 88 L/71 (which is its mid gun) and the shells are cheap too, so this tank is easy to keep in black numbers, at least on the test. The frontal armor is amazing. Yes, it is not as amazing as on the Superpershing, but it has one massive advantage: the sloped part "eats" HEAT shells, they almost always bounce off. I bounced 2 gold shells in a row from a Chinese IS-2 (I know they were gold because the guy told me), that's like 300 nominal pen. Another amazing thing is the depression, it allows a lot of nice tactical maneuvers.
There are two big disadvantages though: the vehicle is nimble but it is slow and accelerates... not that well. Feels like a bit nimbler Panther II, which it definitely outperforms. Second is the turret and hull side armor, which is very weak and anything penetrates it. It's definitely NOT a brawler, more like a sniper. You won't lead any assaults with this tank, but if covered sufficiently by "bigger" targets (your heavies), you can do a LOT of damage. Also, the combination of the powerful gun and frontal armor makes the vehicle completely superior to anything below its tier to the point of absurdity - on long range though. On close ranges, the vehicle's chances are much, much lower. Unlock-wise, if you have the 88 L/71 unlocked from other vehicles (like I do), you can get it straight after getting the tracks, which is definitely good, as the extra engine and 90mm gun will take a while to get and the stock 88mm L/56 is totally hopeless on T8 even with gold shells.

Either way, it's a definitely enjoyable tank.

Leopard Prototyp A and Leopard I are basically the same tank with improved stats. The armor is nonexistent - you don't even have to bother with angling, whatever hits you goes thru, apart from some random high-angled shots. For Leopard Prototyp A, the 90mm gun left over from Indienpanzer seems to be the reasonable option, because its shells are 4x cheaper as those for the L7 - of course, they don't penetrate nearly as much, but as a flanker, you can afford it, because you'll be firing on the side hulls.
That's right: the Leopard, while it looks amazing (like a proper MBT), is NOT a battle tank. You can't slug it out with brawler specialists on close range, T-62 will chew you to pieces. You need to keep your distance and move a lot. With that being said, I think this tank will be the target of a lot of whine, because if you play it improperly, you will die. A lot. I didn't notice any serious problem with the ammorack with it (despite the fact it's situated behind frontal armor, at least in reality), but the driver seems to die often. If that happens, you HAVE to revive him, because immobile Leopard is dead, period.
The depression is kinda okay for this tank, but there are two not so obvious things to worry about. First: the silver shots for the L7 are classified as subcaliber, which means they lose a lot of pen over distance. Keep that in mind. Second, the "adhesiveness" of the Prototyp tracks is somewhat low. That tank drifts a lot, keep it in mind when driving downhill from El-Halluf.
The acceleration is not exactly spectacular, it's not a T-50-2, but on flat surface it catches speed quickly.

Will I level it up? At this moment, I'd say yes. Of course it could recieve some nerfs and we'll have to see, but the vehicle is nimble and thoroughly enjoyable. This is what I want a medium tank to be.