Has anyone heard much of his work? He seems to be quite the dominating force among contemporary composers, especially from Finland.

I have played his music quite a bit. In Lahti they play much.

Kalevi Aho is highly regarded in Finland. He has written 14 symphonies, none of which I know!
Of special interest to us Sibelians however is the restoration that Aho carried out on Sibelius's 'Karelia' music in 1997. Sibelius had destroyed parts of the score in one of his fits of self-doubt. Vanska recorded the completed 'Karelia' music for Bis.--kp

I can't seem to find the Karelia music. I would guess it's at least in one of the Sibelius Edition boxes, though, so no worries.

I just ordered the CD including the 9th symphony and cello concerto. I'll have thoughts on it once I get it.

Ondine ODE 913-2 completed by Kaipainen

BIS-CD-915 compl. by Aho

How to summarize a composer whose style and range are so great - symphonies, chamber, operas…? All written with great skill! Some pieces remind me of Shostakovich or Nielsen, others not at all! - Many of his scores call for vast forces and some are ferociously difficult to play (one of the symphonies [No. 6, I think?] caused a scandal when orchestras refused to play it because it was too difficult). It doesn't sound at all like Sibelius. I especially like the very atmospheric flute concerto.

He has indeed done a completion of Karelia, and of many other works by Sibelius too - the D minor Piano Trio movement from 1889, Ljunga Wirginia, etc. And Aho has also completed works by such composers as Klami.

Aho's Karelia is on BIS-CD-915 (as Harri M rightly points out) and is in the newly issued Box 8 of the Edition (CD-1921/23) along with an alternative version of Tableau 7 (a world première).