I'm perhaps biased as have a friend as a childminder whom my daughter has been with since 7 months (she's now 2.5yrs) she adores her.
In answer to your questions..
It's all down to personal preference. These are my personal views (obviously) and am sure other's will disagree.
Personally I wouldn't entertain a childminder with her own children of a similar age.
You have to share similar parenting views and values.
Example being if my dd is messing around with her lunch or says she doesn't like something (that the childminder know's full well she does) then she wont get her desert or any treats later. Simple as. CM 'rules' with calm and stern (perhaps old fashioned) way, the children know how to behave and what to expect. She will tell them they've been naughty and point her finger and they 'jump'. I like this - I know my dd will stop when she is told to and not run away etc. Other's may not like this approach.
You have to want your child to be in a home environment. I want my daughter to view CM as a very, very special person in her life and I feel no jealousy that my dd has been know to 'cry' for her CM when she's having a tantrum or I'm not giving her something she wants. Other's like the 'professional' setting of a nursery and staff etc.
Personally I see childminders as at least equal to a nursery practitioner - but then again perhaps it goes back to my first point - I like an 'older' old fashioned person maybe with experience of having children and grandchildren and sometimes I view nursery staff as young women without. (apologies, as I say, these are my views)
Support wise.. as far as I'm aware my CM has a monthly meet up with other CM's in area - ofsted and all the paperwork and hoops they have to jump through seems bonkers and off putting and not a support. I'm not sure when you say 'we can support them' who do you mean? I'm thinking on a personal level that I clearly must support my CM in the part that she's playing in raising our child. If dd is happy or has done something or talks about something they have done I tell CM she loved this or that or x or y, yet similarly if CM tells me dd has done something wrong or didn't do this then I will talk (as much as one does/can to dd) about why she didn't do this for CM or why she did this.. is that the support you are talking about ? Clearly parents must support their CM in order for the relationship to work ? DD is with CM for a significant part of her week and if we just spent our lives contradicting everything each of us installs in our child then it would never work.
I could write an essay on the subject clearly! Sorry if I've not been specific or if I've not expressed things particularly well - feel free to ask for clarification or further information if you like!