Just to add onto what everyone said before- just to save me typing it all again lol!
Neutering will ultimately lower the sexual hormones in your buns system.
So, ultimately a change in hormone levels could result in a change in personality. Lowering the amount of sexual hormones (by removing the source- testes, uterus), ultimately and usually will lower aggression, dominance, and some behavioural issues, which usually arise from a high level of these hormones rushing through their systems. The place to start with an aggressive bunny or behavioural issues, is with a neuter/spay, as it really can sort these problems like 'that'.
However, very occasionally this can lead to a 'bad' change in personality; perhaps less cuddly, or even some bad behaviours arising (this is very uncommon though), but it is possible that neutering/spaying can change a very cuddly, needy, and social bunny, into a slightly more independent one.
I wouldn't worry too much about it. It's quite rare, but it is good you are aware of it.
Ultimately the pros to neutering/spaying totally and utterly outweigh the cons to neutering/spaying, and any 'bad' side effects are so rare, they aren't really worth worrying about too much.
Also, buns can hit their 'naughty teen' stage (mentioned previously) at about the juvenile age of 6 months- right when you spay/neuter them, so a change in personality for the worst, may be nothing to do with the neuter/spay, and just their personality naturally changing.
Having never experienced this 'naughty' stage, I can't really give you much info on it, but I'm sure someone with experience on it can come and give some info
:bunnydance: Jen