JRR, I wince when I read your comments. There are a few good reasons why someone might want to avoid this game, but disliking the dice system isn't one of them.
FFG is selling separate die sets, so your concerns about replacement are unfounded. And sure, if you leave your dice at home you won't be able to borrow from your friend to play, but you have to remember--this is a boxed set. Just keep your dice in the box with the rest of the game, not in your dicebag. And if you do forget your box, then you aren't playing anyway, dice or no dice.
As far as knowing what you need to roll to succeed, well, you just need to roll at least one net success. It's as simple as that. Admittedly, calculating the probability of success is tricky, but that's true of any rpg system where you roll multiple dice, from Gurps to Storyteller to Savage Worlds.
Anytime you're not just rolling a d20 (or it's higher resolution cousin, the d100), the best way to judge your odds is by calculating the average expected results-- For example, if your D&D greatsword does 2d6+6 damage, your average damage is 13, or if you're rolling 9 dice in a storytelling system game, you'll average 3 successes.
WFRP3 is no different:
[sblock]blue (characteristic) die: +1/2 success
yellow (expertise) die: +1/2 success*
purple (challenge) die: -3/4 success
red (reckless) or green (conservative) die: +3/4 success**
white (fortune) die: +1/3 success
black (misfortune) die: -1/3 success
[/sblock]
or, if you're more concerned about boons:
[sblock]blue (characteristic) die: +1/4 boon
yellow (expertise) die: +1/2 boon*
purple (challenge) die: -3/8 boon*
red (reckless) or green (conservative) die: +1/8 boon**
white (fortune) die: +1/6 boon
black (misfortune) die: -1/6 boon
[/sblock]
So someone rolling: ♦ ♦ ■ ♦ ● ■ ■ averages 5/6 successes (less than one, so not quite even odds of success, but pretty close) and 5/12 boons (closest to zero, but more likely to get a boon than a bane)
* converting the critical success and critical failure symbols to normal successes, boons, or banes, as they would be if there were no specific critical effect related to the action
** rounded for ease-of-use