The sum of Maazel's VPO recordings of the Sibelius symphonies is greater than its parts. His interpretation of the 4th is, arguably, the definitive recording of this work - other performances always sound slightly hesitant by comparison. The 7th is also a majestic, profoundly moving account of Sibelius's late masterpiece.
Maazel's 3rd and 6th (which were coupled on the original LP recordings) have attracted mixed reviews due to the generally faster tempi, but it works. The strength of the scandalously underrated 3rd lies in its relentless drive towards that glorious, final C major chord and Maazel ensures that the feeling of momentum is never lost. The 2nd movement of the third also benefits from Maazel's faster tempi, turning it into a delightful waltz. As for the 6th (my favourite Sibelius symphony), for me, this is also a definitive recording.
Maazel's performances of the 1st and 2nd symphonies are perfectly good - not the best recordings of these works, but by no means the worst. If it wasn't for Maazel's 5th, this might be the best boxed set of the Sibelius symphonies.
It's curious how a conductor who manages to get it so right in the 4th symphony can manage to misjudge the 5th so spectacularly. Karajan had the measure of the work, slowly building up the tension without losing any momentum. Sadly, Maazel's 5th lacks the grandeur and primordial, raw power of Karajan, Rattle and Berglund and he performs the symphony like a man in a hurry.
In conclusion, for slightly more than the price of one CD, you'll get at least two (I'd argue four) definitive performances and only one dud. Maazel's 4th alone makes this a five-star offer.
Perhaps the age of the recordings might put you off, but the sound quality was always impressive on vinyl and these remastered interpretations are even better. If you love Sibelius, this boxed set is a must.