My two cents: While acceleration may not be the ideal solution, the cost of NOT accelerating may present more negatives, such as:
- lack of challenge leading to boredom,
- loss of sense of discovery, exploration, curiosity,
- development of an unwillingness to struggle and risk making mistakes,
- dearth of opportunities to learn from one's mistakes/failures,
- failure to develop perseverance and resilience,
- lack of respect for other people and their struggles/failures.
- More at this post.

Adding a link to a thread called what kids don't learn, which contains an article listing 10 essential skills which are developed through effort, such as experiencing appropriate academic & intellectual challenge... skills which people may not develop without this level of challenge.

A single-subject acceleration (such as math) affords the child the opportunity to be with academic/intellectual peers for math while also spending some time with chronological age peers for other subjects.

Here are some links to old forum discussions which may be of interest:
1. Thread called Polling Davidson forum members on acceleration, which discusses whole-grade acceleration (grade skip) and has many links to other threads with thoughtful responses on children's experiences with having older friends/peers/classmates. A list of these links is also summarized in this post from a thread called Considering a grade skip.
2. Post linking to "The Right Fit" authored by Tamara Fisher, from archives of her column Unwrapping the Gifted, for Education Week.

Bottom line: Think in terms of matching the program to the child, rather than matching the child to the program. Take each year at a time, and adjust as needed to facilitate your unique child's academic, intellectual, social, and emotional growth and well-being.