we have had about 6 rounds of botox over 2 to 3 years (basically every 6 months) so far with our son. Good results although the last one was 2 weeks ago and we are still waiting to see the effects.
Funnily enough, my son has such high tone and the botox doesnt show improvements in measurements but rather in functionality ie sitting to standing, walking independantly. The only problem is for Daniel it wears off very quickly and the functional improvements gained are sometimes temporarily lost - VERY frustrating for both him and us!
In NZ they undergo a general anaesthetic for admin - we found over the years that for Daniel a pre-med was a must as this made him much less grumpy coming out of the anaesthetic. We also tried serial casting - about 3 times but this was a failure - Daniel had such high tone that he even managed to push one of his casts off with his feet!! Even the orthopaedic surgeon tried to cast him but they could never get the ankle in the right position - his foot would just slip out of the cast! The botox seems to not be working as well now, I have heard this happens over time, and for Daniel only lasts about 6-8 weeks so we are fighting for the interim to get it more frequently (this time was at 5 months, it has been suggested by another medical specialist every 4 months. )
This specialist had also been to a spasticity lecture and information from this was that there were no long term side effects of frequent botox in children which is good.