We bought our first Jazz in January just gone. Whilst researching the model prior to buying I was told by someone on another forum, a knowledgeable chap who seems to know his motoring onions, that the I-shift is "horrible".
Our previous car was a Ford with Powershift, which is an over-complex autobox with a reputation for catastrophic failure. After that experience I was determined to avoid any automatic which has had even a sniff of bad Press, so we tried a Jazz with CVT, and found that gearbox seamless but uninspiring.
Hence going for the manual which as said elsewhere, progresses adequately but definitely needs a sixth gear.