This was originally a response to another post concerning Sibelius, but my response became more about Bruckner than Sibelius, so I figured it was worth making a separate thread for it.
Regarding length, I find Bruckner's music is very cyclical and even a bit OCD but the tension-release certainly originates in a much more natural mechanism than Sibelius, probably there's every bit as much of the Schubert-Beethoven tradition in his work as there is Wagner.
Maybe, but beyond the influence of Viennese composers of the previous generation, the essence of Bruckner's craft was sacred music; this is what sets him apart from other composers at the time, with the exception of Liszt who was also an ordained priest, but who lacked Bruckner's humility to be able to write music as meditative. To me the reason why his symphonies are enjoyable at all is because he treats the orchestra like an organ, orchestrating in large blocks that mimic the combination of different stops on an organ. This is similar to Wagner, but without the voices and solo passages for section leaders to break up those taxing full orchestral textures.
But I'll say here what I've said before about Bruckner; since all this is the case, why not go straight to the source and listen to his sacred organ and vocal music, which shows his two artistic strengths, contrapuntal mastery and a profound understanding of religion and its associated musical history, in full force? From my perspective, people's praise of Bruckner symphonies looks like someone listening to "Domination" by Morbid Angel and enjoying it; there is a whole separate part to their output that unless you address, you aren't really evaluating them fairly, and many people do the same with Sibelius. You haven't heard Morbid Angel until you've heard "Blessed...", you haven't heard Sibelius until you've heard the fourth symphony, and you haven't heard Bruckner, indeed perhaps you've not lived at all, until you've heard this:http://www.youtube.com/watch?v=FkTUK0nEtco
"Os justi meditabitur sapientiam,
et lingua ejus loquetur judicium.
Lex Dei ejus in corde ipsius:
et non supplantabuntur gressus ejus. Alleluia."
"The mouth of the righteous utters wisdom,
and his tongue speaks what is just.
The law of his God is in his heart;
and his feet do not falter. Alleluia"
Terse, cogent, and passionate, compared to the symphonies, which are drawn-out, and passionate only.