I think John's problem is more to do with excessive and unecessary use of police weapons. From what I know of the police officer and the CS spray incident, it appeared to be most unecessary. Also in the USA there have been several cases of people dying as a result of being hit by a taser.
According to Amnesty international tasers have been used there against,
"unruly schoolchildren, pregnant women (one of whom lost her baby afterwards) a 71-year old half-blind woman and startlingly, a 9-year-old girl who was already handcuffed." http://www.amnesty.org.uk/ni/news/080306.shtml
We need to at least weigh up the pros and cons, it may prove too easy to use a taser, and lives may be lost as a result.