Given this memorable melody, this piece would be exciting whether it's slow or fast. Even if you played this very quickly, you can keep your audience captivated, although you might miss many opportunities to speak. If played more slowly yet with the utmost expression --- as it is played here --- it can produce a huge effect and keep you just as captivated as the next fast version (unless what you are looking for is a rush of adrenaline rather than more depth).
I love Kissin's playing. It is clear like crystal, and he does the rubato in just the right places to make it sound "just right". Perhaps there is a reason he has not made another recording of this piece: that he cannot surpass the musicality of this piece.
Karajan's Berlin strings positively mesmerizes. Sometimes their entries are so full of feeling that they nearly break your heart. Towards the end of Karajan's life, the strings are more beautiful, yes, but actually - they were just that much more expressive. Every violinist is doing vibrato to the extreme, and you get a tender, heart-wrenching sound out of them. I think this is what this piece called for.
Besides, I don't think the tempo was too slow at all. Kissin's virtuosity still shines through. Especially in the 3rd movement. Don't listen for the virtuosity though. Listen for the musicality. And you'll like it.