Rav Nahman of Breslov was against learning any kind of philosophy and I can see his point being that it never comes to any kind of conclusion. You can spend a lifetime just trying to untangle the arguments and still have gotten now where. However the Kant-Fries-Leonard Nelson system has found a certain amount of grace because in it there is a justification of faith plus an accurate way of showing the limits of reason and the limits of faith.
I mean, you can see to a great degree that just Torah with no Metaphysics at all tends to be a bit too narrow. It leaves too much room for delusions in areas that are not within the strict bounds of Gemara and Tosphot.
But as far as Rav Nathan was concerned, the opinion of Rav Nahman was also against learning science and that is far less clear based on many places in the LeM where he emphasis seeing the wisdom in all things including physical. Plus his emphasis on faith in "the wise" {LeM I:60}. And that would have to include the gedolai Sefarad like Ibn Pakuda and the Rambam.
[I have to mention that the way of learning fast by saying the words and going on makes the most sense to me in this regard since not everyone is an Albert Einstein, and yet the way Ibn Pakuda and other rishonim hold this kind of learning is an obligation. So the path of fast learning is the best idea. However some sessions of review are also important, but how much to emphasize one kind of learning as opposed to the other is not clear to me. In places like the Mir in NY and Shar Yashuv, it was thought that depth learning is for the morning and fast learning for the afternoon.]
