I have seen quite a few characters who dipped into the class, but none who took it more than level 5 or so.
The class is very nice, and its auras are very powerful, but after a few levels in it you just dont get much more punch out of it.
As a prc in the last campaign I helped the marshal character come up with the following:
HD: d6
BAB: poor
Saves: F: Good, R: Good, W: Good
Req: 1 minor and 1 major aura, skill focus(perform)(any), perform 8 ranks, must speak at least 10 languages
Class skills: same as marshal
skill points: 4+int mod/level
Weapon and armor prof: nothing new
1: Minor aura boost (+1)
2: Inspire animal, Expanded aura
3: Major aura boost (+1)
4: Extra minor aura active
5: Minor aura boost (+2), major aura boost (+2)
6: Radiate courage
7: Minor aura boost (+3), major aura boost (+3)
8: Inpire excellence
9: Minor aura boost (+4), major aura boost (+4)
10: Extra major aura active, Minor aura boost (+5), major aura boost (+5)
Minor aura boost: all minor auras gain this bonus in addition to all other bonuses it may get.
Inspire animal: animals also gain the benefit of any auras this character has active if he so desires.
Expanded aura: Aura radius is expanded by 50%.
Major aura boost: all major auras gain this bonus in addition to all other bonuses it may get.
Extra minor aura active: the character may have two seperate auras going at the same time (in addition to a major aura).
Radiate courage: immune to fear and fear like effects, all allies which are effected by any of this characters auras also gets a +4 morale bonus vs fear.
Inspire excellence: A number of times per day equal to his charisma bonus this character may inspire excellence in all those effected by his aura. He must expend a full round action, at the end of which everyone, including himself, has a +2 perfection bonus to saving throws, attack rolls, damage rolls, and skill checks. This bonus lasts for a number of rounds equal to the characters charisma modifier. If a creature no longer gains the benefits from any auras then the bonus is lost. No character may recieve this bonus more than once an any given hour.
Extra major aura active: the character may have two seperate major auras going at the same time (in addition to minor auras).
I dont know if it is helpful for you or not, but we certainly liked it and it didnt come off as being too powerful (sort of a different, non-spellcasting bard).