I agree- it depends alot on the child, etc. Some kids become so depressed and shut down so much if they don't skip, it's better to skip. Some kids can still function, esp. if their school has enrichment, a good G/T program, etc.
If you look at some of the posters on this site who talk about ADD, etc, some of these kids have been skipped and are 1-3 years younger than their agemates. obviously, ADD is a medical diagnosis, so these could be kids who have ADD and that's it. I will not mention the posters' names since you can see them in old archived messages.
However, I mention this issue since it's something parents may not think about in skipping their 5-year old to second grade. The homework level and the pace in school goes up alot each year, and by 6th grade, etc. it can be overwhelming for even gifted kids. My son tested on the math part of the WJ-III in first grade into the 8th grade part on alot of it, yet he's sat tight (slightly bored but stable) working on speed math tests, since that is what the school wants from him now.
Our gifted program starts in 4th grade and is full-time. It seems to be very good- they kids skip 1-2 grades of math in it. What if we had absolutely nothing for him, which some posters on this site tell us they have? Maybe skipping would be his best option. It obviously depends alot on the child, the family, and the local resources.