^{Update by Mega_Spud:}
Summary:
A single piece of coal should be able to smelt 8 items. When a hopper is used to feed different items into a furnace however, there is a fractional delay in the process that means only 7 items will be smelted per piece of coal.

Steps to Reproduce:
Using the setup as pictured here:

1. Build the setup as as pictured
2. Place the items into the chests
3. Wait for the furnace to use up the fuel
4. Notice which items get smelted

Observed Results:
Only 7 of the 8 items will be smelted, as they are fed into the furnace via a hopper.

Expected Results:
All 8 items should be smelted.

Screenshots/Videos attached: Yes

Notes:

Original Description:
I set up a furnace and put three hoppers to it. I start cooking various items and the sum of them totals a number that is divisible by eight. I put in the exact amount of coal needed to cook all the items, in every other version of MC I've played (ps3 and java). (Edit: For complete clarity, this report is about the Win10 version of MC.)
The coal ran out, and there were still items left to be cooked. So something isn't working properly with the tick timing for pulling things out of a chest and putting a new item in it automatically with hoppers and chests to maintain the eight items cooked per coal, 1 item cooked per two sapling, 3 items cooked per two wood as fuel.
Water update looks awesome though!

EDIT: I got screenshots of my setup. Please note, that I tried with and without the lever and I got the same result, but only took screenshots of with the lever because that's the only way I could pause it long enough to get a screenshot of what is going in the "to cook" chest.