We caught a boat from from Portovenere. The Euro4 boats are very uncomfortable with wood lat seating too narrow and short in the back to provide anything but discomfort.
Monterosso is the furthest and largest of the villages and takes 1hr 15 mins to get there. The village is one big tourist trap given over to a myriad of mediocre restaurants and other ways to spend your money on tourist tat.
It's moderately attractive (no cars) but there are hundreds and hundreds of villages across the southern Mediterranean that are much more attractive. The only near-unique thing about Monterosso is that it is only accessible by sea or rail.
We disembarked next at the next village down (Vernazza) but it was just like Monterosso but on a smaller scale. Warning, disembarkation and embarkation at these smaller villages is hazardous if the sea gets a bit choppy. My sincere advice is to stay well clear of the boat trips on anything but totally benign weather. With the slightest swell in the sea you can be abandoned to find your way back by rail and then bus/taxi or of course walk many miles as the boats can't get close enough to the rocky shore.
I guess the only attraction is the trail walks. The scenery between the villages will be good if you're young or fit enough, (but many of the trails were shut because of landslides walkers told us).