Eggy - my speed is increasing well, which I suspect over a 10k or even a half would be very beneficial. But on a long run I seem to be running out of steam. I ran a 20 today (the only one I'll do) - and my goal was to keep my heart rate 135-142. I managed that for about 14 miles or so at a pace about 45 secs slower than MP, and then my heart rate steadily climbed for about the same pace to 155 or so. And now my legs are tired - more tired than my long Comrades training runs (granted, they included quite a bit of walking).
All stations have fruit of some kind, then as Becca7 says, some have other things too - including potato chips, potatoes, sweets etc. Spectators will have an endless array of foods that you can have too.
It is unusual to see a runner carrying their own supplies as there is so much available except for gels
Don Oliver makes this comment: if you haven't walked in the first hour of Comrades, you've made a grave mistake. I think for anyone slower than a silver medal, this is probably true. And it's not easy to walk in that first hour as you simply feel to good. Of course, in 2015 it might be easier, as Berea's hill is right there at the start.