I was leveling in bibiki last night and since i noticed that there was a bard in the party when i got invited in jeuno i picked these up out of my mog house to try them out. After I leveled last night and my evasion skill went uncapped again i looked into my combat skills list and my evasion skill was still the same, with or without the earrings. At the time i looked i had Paeon and Ballad on (was too close to the mages :P) I looked again at my combat list again about once a fight for the next 5 or so fights with no change until my evasion just naturally capped itself out. Mebbe i just got defective earrings =P
Speaking as a Lvl 67 Bard I can count the number of times that I have pulled hate on one hand. The fact of the matter is that if the tank voke quickly from the start of the battle its almost impossible for a bard to take hate from him.
Note that these earrings are one of the few items to boost evasion *skill* rather than evasion *stat*. It's easy enough to tell the difference - skill boosts will change the number in your combat skills (these earrings do only change the number while you have at least one song on you), stat boosts will not. Most "evasion+" items are stat boosts.
Evasion stat is the AGI equivalent of DEX's accuracy, STR's attack, and VIT's defense. As a result, boosting the stat generally seems to be more effective than boosting the skill, so it's just as well that most evasion+ items boost the stat.
In this case, though, it's a little different. Boosting evasion Skill is like boosting a weapon's skill or boosting elemental magic skill. It's much more effective than just Boosting INT or AGI. Skillcaps raise, and monsters become weaker and weaker compared to a player's enhanced skills. Having these equipped as a Ninja is the equivalent of having the Evasion of a Ninja 2 levels higher than yourself (or 3 if you're in the 50s). It helps a LOT and I've noticed a considerable difference. I've heard that 1 Evasion Skill point is roughly equivalent to 2.5 Evasion stat boost, but I haven't been able to confirm this yet.
Definitely worth the 48.000 each, i had to pay for them :) CHR-earrings are rare and nice for bards and beastmasters, but the extra Evasion bonus is especially great for farming bards.