I'm sure that this review won't make any difference - loads of people will buy this, because it's comprehensive and cheap - but there are reasons why you should go elsewhere. The most important point is that Fischer messes with Haydn's music in almost every symphony, by making certain passages solo strings only. (How do I know this? I'm a Haydn anorak, and I know all the symphonies off by heart. Not a bad thing to be.) Haydn did like the sound of solo strings, but he says when he wants them. They're all over the place here. That wouldn't matter so much, except that whilst the sound of the orchestra as a whole is fine - clean, with little vibrato - the solo strings are syrupy and sentimental. As a result, many of Haydn's most sublime moments are turned into salon music. This is a serious point: nobody would get away with doing this to Beethoven, so why accept 'Haydn with custard'?
Apart from this, the performances are not bad - symphonies 1-12 are best, with all repeats, whereas Fischer ignores second-half repeats in the later works. Dorati, surprisingly, is better repeats-wise.
If you are interested in buying Haydn in better performances, try Harnoncourt (various ones, including the last 12) or Hogwood (nearly all). Or above all, Bruggen really makes the music speak (he has recorded the 'Sturm und Drang', 'Paris' and 'London' sets), who also offers us the original version of the Finale of No. 103 ('Drumroll'), which is far better than the truncated Vienna version that everyone else plays. And don't touch Beecham, who makes cuts in what were already corrupt texts.