That is very wise.
Almost everyone I know who started med school with a specialty in mind changed their opinion at least once.
Not surgery mainly because I've found surgical specialties to be often comparatively hierarchical, and also because my surgical friends seem to have a poorer work-life balance. Whether they're an reflective sample, I don't know, but that sort of life isn't for me.
Heh, I love GPs. But I don't think I fancy GP as a career (and I did think about it quite hard, because I'd like for it to be my thing!)