The Jazz handbrake inefficiency has been commented on before.
I am on my third Jazz, two GD's and now a GE and the handbrake has not been a cause for concern on any of them.
My only comment would be that when pulled on hard the lever feels very spongy and does not inspire confidence but it does work on quite steep hills.
I also leave any car in gear but that stems from also driving automatics that are left in 'Park' as well.
Vic.