The first time I read it, it was awesome. The ending was very very nice, and something of a twist, but that was actually cause you were only expecting a twist.
The second time, it was still good, although I paused several times in completeting it. I read a different translation for the final chapter, and it took away some of the coolness of it: the first 1: "Can you make my heart flutter once more?" Second one: "Can you excite again?" Not as cool.
I have to say, now that I'm thinking back, the series doesn't seem too fun. It seems to me that the ending leaves something of a bad taste in people's mouths, which is why it recieves such bad scores. I personally think that the ending is very nice, although may have been better and different. A real slice of life ending.
The more times that you read this, the worse it'll get, basically. The ecchi is one of those "ha...." things, where it's fun to see but basically feels even more useless than average fan service. The man character is just plain annoying, damn, the indecisiveness the made way too freaking apparent. They added way too many girls in the series, probably 2-3 more girls than the series needed.
Art is awesome, just plain awesome. The mangaka is one of those very beautifully styled artists. Always between B+ to A for this artist, particularly for the girls.
The comedy... as said, is a bit based on the ecchi factor, which sort of sucks. The real laugh out loud moments are few and far between, although they exist.
There's actual romance in the story. Harem-ecchi-romance-comedy mangas are sorta... bad at that, honestly. Everyone in a generic harem-ecchi-romance-comedy is basically some incarnation of Love Hina characters, a general tsunade, but the character development in Ichigo 100 is there. Only satsuki's really a tsunade, and even that's gone later on.
And speaking of satsuki... damn, I hate the author for that. I mean, she never even had a freaking chance, did she?