My daughter went to a childminder from 6 month to about 17 months. Loved it, couldn't fault it. She had a great balance of staying at home, painting, gardening and general messy play with days out to farms, parks and baby/toddler groups. I loved the fact she was out experiencing new things and still getting the nice home setting - I don't feel like she missed out on anything by us having to work.
We moved her to a nursery around 18 months purely because the childminder retired unexpectedly. She's been there about 5 months now and I really miss the one on one with a childminder. Everything was more personal, a childminder knows your child better than nursery staff will purely because of ratios. We got a full report from the childminder every day, told us about her moods, what annoyed her, what she loved - loads of detail. At nursery, it's a quick one minute run down read off a whiteboard that might be read by somebody who doesn't really know them. Perfect example, my daughter has a dairy allergy and a member of staff told me she had salmon with cheese sauce followed by chocolate cake for tea which was obviously wrong!
She's also either in the same room or garden every day now and her routine had to switch to fit with what works for the nursery, not what works for her. However, her speech is fantastic since starting nursery, her table manners have improved because she's sitting at a table watching her peers and she does seem to be learning new things all the time.
The only thing you need to consider with a childminder is holidays. If the childminder is off, you will have to be off. If the childminder is sick, you'll have to be off. You're essentially reliant on one person, whereas nursery doesn't have that problem.
Our childminder was £40 a day, nursery is £52 a day - another thing to consider!
With the next child, I'll definitely send them to a childminder for the first year at least.