Mine is a success story so far as well!
In my opinion, a manager doesn't organise the day to day running of a band, they are your connection to the industry! You employ them for their contacts and their savvy! Touting you about to the people who matter, getting people talking about you etc!
Their job is not to get gigs or tours (although this does happen sometimes as a bi-product), their job is not to get you rehearsing, it is not to run your myspace!.
Further down the line they will organise and run your diary, but that's about it, they will then start to organise an infrastructure of people around you. Agents for gigs, Tour Managers for tours, Press & PR people, Endorsements etc etc
They will of course make sure you are meeting the deadlines you are supposed to meet, and kick you up the arse once in a while, but it is down to the band to sort their daily routines IMO! (I'm talking at toilet-circuit level).
It seems to me that any people that have had negative experiences have usually done so because:
A ) it was their brothers cousins dog who was doing it, not someone with decent industry contacts
B ) they believed that EVERYTHING was to be done by the manager
C ) didn't have the contract checked out well enough and were stitched up
D ) they simply didn't 'make it' and are bitter
All of these things are very easy to overcome of you stay on top of the day-to-day running of your own band!
But realise that not many people within the industry will take notice of a 'self-managed' band contacting them, unless they have a massive following and simply can't ignore them.
Each 'scene' within the music industry is very tight knit, everyone knows each other, and so having a decent manager within those circles is priceless!
Si