My 21 month old is due to start nursery in September for two days a week, around 8am-3.45pm, while I'm at work. We did try nursery briefly when she was around 12 months old, and gave it several sessions of around 2-3 hours a couple of days a week (perhaps not enough) but she was very upset and we decided to reconsider at the time as we had other options.
Since then she has really grown in confidence and is more used to being looked after by people other than me, albeit not for quite as long. I would say she is still quite sensitive, but not so much around other children (she has an older sibling). Around the time she first tried nursery she would be upset if I even went upstairs and she was downstairs with DH, whereas now he or grandparents can look after her and she'll usually happily wave bye if I go out of the door or can be easily distracted if she does seem unsure.
I love the nursery and feel she'll be very happy there in the long term and that on balance it will offer benefits to her, but feel absolutely conflicted about the settling process. I know she will cry at drop off but what I'm worried about is her being distressed throughout the session. It doesn't help that financially we are worse off for me working those particular days in short term (and I will be working extra weekend shifts elsewhere to cover the childcare cost of the week days too) and so the benefits aren't obvious but long term it is an investment in retraining and thus should hopefully benefit her in terms of future security and opportunities.
I have considered childminders but there aren't any available that have been personally recommended to me (whereas I know many people whose children have been very happy for years at this nursery and it is a reasonably small setting which otherwise I think meets her needs better than others I've looked at).
I would love to hear how other children have got on starting around this age, as it's weighing on my mind a lot.