1. Every time we saw a black hole created, there was great heat involved. . . Supernova, Core of a planet, matter/antimatter explosion. . . plus, if you are going to destroy a planet using a black hole, the most efficient way to do it would be from it's center. . . see:
http://www.youtube.com/watch?v=QEhn--ys7rU&feature=related (so, no this is not a plot hole)
Heat can't be the issue. The core of the Earth is only about 5700°K, while a plasma torch (20th century technology) is about 25,000°. Surely there would be an easier way to generate sufficient heat that drilling to the planet's core.
2. He calculated it. . . there were cut scenes from the film that showed that. . . shrug. . . ymmv, but it's not a plot hole
Calculated it how? Black holes have never been used for time travel before, so how can anyone possibly determine the exact time and place someone will emerge from one, especially after inadvertently getting sucked into one without a pre-determined course and speed?
3. Spock lives on Romulus, he's the Federation Ambassador to Romulus, his life's work after StarFleet has been to reconcile the Romulan and Vulcan peoples (per ST:TNG episodes Unification I and II). . .the Romulans and the Federation allied during the Dominion War. . . and the destruction of Romulus probably destablizes the Alpha and Beta Quadrants. . .plus, according to the narrative in the movie, this super-duper hyper nova was going to destroy more than Romulus. . . so why not help them? as for why Romulans didn't save their own world: they didn't believe they were in danger. . .bureaucrats, government ineptness, etc. . .(Read Countdown). . . it happens. . .sorta like Hurricane Katrina caught so many people by surprise -even when they had been warned. . . (so, not a plot hole)
I don't have a problem with the Federation being friendly enough or self-interested enough to help the Romulans, I just don't understand why the Romulans can't help themselves. But if the Romulan government couldn't be bothered to save itself, why does Nero blame Spock for not saving Romulus? Shouldn't he really be angry with the jackasses in the Romulan Senate for sitting back and ignoring the problem, instead of at Spock who worked tirelessly to save them?
4. Not as big of a coincidence as you might think. . .Nero wanted Spock to not only see his planet destroyed, but wanted him to live with the pain of losing his people. . so he put's Spock down close enough to the Federation Base to survive, but not close enough to it that he can warn anyone who might be there. . .nu!Spock puts Kirk down close to the Federation Base and the computer warns him that it is dangerous out and to wait to be picked up (which he promptly ignores and heads off toward the base -- so he and Spock are in the same vicinity at the same time). . . as for the snow monsters. . . Spock had a fire. . . and since the snow monsters were afraid of fire, it would make sense that he and Kirk took torches with them to wave the monsters off. . . not a plot hole.
Why would Nero want Spock to survive after Vulcan got destroyed? Wouldn't it make more sense to just go back and get him, take him back to the ship, and torture him some more? Wouldn't Nero want to watch Spock's agony as he saw his home planet destroyed? For that matter, why did he send him down to the planet in the first place, instead of having him watch it from the ship? How did Nero know Spock would even be watching, instead of hiding in a cave, like he was when Kirk found him? How did Nero know Spock wouldn't be eaten by a snow monster?
And if Spock had "fire" and knew where the starbase was, why didn't he just go there himself, instead of hide in a cave? For that matter, how did Spock even know he was near a starbase? Even if you assume he remembers the location of all the starbases from 150 years ago, he doesn't know where on the planet he is, so he should have no idea where the starbase is. And if you assume that he was close enough to the starbase to see it from where he was beamed down, once again, why didn't he just go there himself? And if he was close enough to see it, Kirk must have trekked nearly 14km through the snow (the distance his pod told him he was from the starbase), and just as he got near the cave Spock happened to be hiding in, the snow monster happened to come out and chase him around, and he happened to stumble into the cave? Give me a break.
5. the black hole formed INSIDE Nero's ship. . . collapsing it upon itself. . . there was no way that it would have survived. . . no way that anyone could have survived to travel back in time. . .so, not a plot hole. . .
So, at what point does something get crushed, and at what point does it go back in time? Obviously, a ship would have jump through time at some point before it reached the center of the black hole (by which point it would be crushed by the gravity), so isn't it surmisable that parts of the ship would jump back in time before getting crushed as well?