True, it would have been tricky to not only hit Spock with the loss of his planet, but, at the same time hit him with the fact that it was done by a planet of Vulcan exiles, it would probably have been a bit too much to deal with in one movie.
Many of the irregularities are at least techno-babbled away, which Star Trek is famous for anyway, though, in all fairness, the whole 'supernova' thing left me feeling a little disappointed, it would have taken a damn big star to 'threaten the entire galaxy' by going supernova, or a chain-event of some kind, that left me feeling a little let down, since it means in the last 3-4 Star Trek movies the score is:
Supernovas : 2 - Generations, Star Trek
Large Romulan Ships : 2 - Nemesis, Star Trek
In all fairness, however, Star Trek does it all a damn site better than Generations or especially Nemesis (More commonly known in these parts as 'The Revenge of Right-Said Fred').