I just finished 2.6 from April 7 (or something) and here's my experience. I have basically finished the game three times: on 2.4 (normal), 2.5 (normal) and 2.6 (very hard).
GeoscopeWhat I probably most loved about this was the lesser number of UFOs. At least I think there were less of them than in 2.5. But this may be just because in 2.5 I ran half a year with the whole globe basically covered. I definitely saw an unwelcome increase in missions after building a fourth and fifth base. 6-8 simultaneous missions is just too many for me. It basically makes the whole game just halt for a day or few (real time) while you clear them out. Eventually I just ignored them (which luckily was not much before I won) with the intention of doing them only when nations started getting content.
Even on very hard I felt like the aliens are just some boyscouts in their toy ships, really... Their ships go down so easy it really doesn't fit at all with the story. My aides are telling me of their superior technology while I shoot them down with my trusty Shiva rotary cannon. The only real hurdles are of course harvesters in the beginning and bombers later on. Other than those I was constantly pretty well on equal playing field with them. One reason maybe is that hybrid missiles are so good (not that I ever ran out of antimatter missiles either). I feel the progression should rather be two Dragons for Harvesters, two Starchasers for Corrupters and two Stingrays for Gunboats. And Bombers you realistically wouldn't shoot down.
One thing I definitely noticed were the longer research times I had. I finished on March 2085 and had a bunch of unresearched stuff. So I really had to prioritize, which is great. But then I started thinking you can really make do without researching a whole lot of stuff. I only did plasma rifle and ignored the rest of plasma weapons. I did electromagnetic rifle and coil gun, and EP ammo. Particle rifle I got just before I won. You only need one autopsy. Then you need to research the UFOs, expect maybe for Gunboat since Starchaser seems plenty good.
One thing that could probably make this portion a lot more challenging is when the XVI gets implemented. I don't know what it'll do but it cannot help you for certain.
Keeping the nations happy didn't seem very difficult either, except in the beginning when I didn't sell one UFO and then got a message that nation happiness is below the allowed for the campaign. Which probably means I lost, but since it was like week two I just ignored it. After that no problem really.
I built a second base right with the starting money and then a third a few months later. Then fourth and fifth only when the aliens brought a lot of particle weapons and needlers. So mostly just ran with three bases; one research, one production, one with a little bit of both, but mostly just for radar. I only had one dropship as well for some reason. Maybe because cash was tighter in the beginning and needed more for labs.
The most exciting moment was when my full experienced squad got shot down into the sea. The missions were definitely more difficult with rookies against particled ortnoks, since ranged combat was a lot less effective. No more Helena Berg's hitting always from the other side of the map. Another exciting moment was defending my production base with a squad of 6 rookies.
Maybe curiously I didn't assault any alien bases. There were some supply ships, but I figured I'd only search for the bases when I got ground assaulted for the first time, and that never happened. Maybe I was lucky. Personally I'm of course quite happy about that, as the alien base missions are a real pain with no in-mission save.
BattlescapeSmoke. That's all you need. When I didn't use smoke, I would invariably lose someone dear to me. It really feels overpowered. The autopsy for Shevaar says they cannot see, but they can sense warmth or something. It would be nice if they behaved like that with smoke. At the moment it feels like they can know you are in the smoke, but they still need line-of-sight to shoot you... The aliens could have smoke of their own, or blindly shoot into smoke or utilize grenades.
Sometimes I didn't use smoke and tried to play with reaction fire instead. It occasionally worked with great results (with aliens coming down stairs for example), but the amount of guys you need for a reasonable chance to kill someone who shows up seems pretty high. They need to be on snapshot or they might die before the enemy. Then the enemy needs anywhere from 2 to 6-8 shots to die, depending, and then your guys also need to hit the enemy... Just feels unreliable to me, but then I'm not really good at this game.
EP ammo seems quite powerful... A lot more powerful overall than the aliens' particle things. The only downside is the normal sniper rifle is not very accurate, and of course they cost a bit. I don't know how the particles compare in accuracy with the assault rifle, but the assault rifle has full-auto... And I'll never understand the aliens' love for the needler. I use it myself because it's fun, but it honestly doesn't do all that much most of the time on either side. In any case, I was mostly running laser rifles and coil guns in late game. The rookies don't hit that much with assault rifles. Overall the power of the alien weapons is about right. A hit from particle rifle on a nano armor rookie mostly was death I think, which feels right. I think the aliens could use another full-auto weapon after the plasma rifle though. Not many carry particle cannons, and I think it's quite inaccurate anyway. And the accuracy of combat hovernets could be increased. They're pretty awesome already, almost always hitting at least once, but they could be more awesome still.
On the endingI didn't even know we'd found a carrier UFO. I DID skip all the reports this game and tried to scan them quickly for carriers, but didn't find anything. Anyway, I guess it's important they know what to shoot at. I don't really need to know.