After finishing Black Cat, I decided to check out some of Yabuki Kentaro's other works. Since I never found Yamato Gensouki, I figured I'd settle for To-LOVE-Ru, even though he only did the artwork and the premise was practically a carbon copy of Urusei Yatsura's.
To be honest, I actually found the first few dozen chapters to be fine. The jokes were largely hit-or-miss, but Yabuki's artwork and the chemistry between the characters kept me reading. All-in-all, it was a typical ecchi harem that didn't really wear out its welcome.
But then, at some point, writer Hasemi Saki lost steam. Her jokes grew more and more bland, losing any semblance of charm there may have been early on. In addition, what little drama there was, she didn't handle very well. Two scenarios in particular (Lala and Haruna becoming rivals but remaining friends, and Rito realising that he has feelings for both of them instead of just Haruna) could've been really good for character development, but their potential is squandered in her hands.
Overall, the series never rises above mediocrity after its initial stretch. Yabuki's artwork is great and the fanservice is fine, but Hasemi never exploits any of her good ideas and her humour becomes repetitive and dull far too quickly. The ending is also extremely abrupt, and is ultimately an unsatisfying conclusion to an unsatisfying series.
I personally wouldn't recommend it to anybody except die-hard ecchi fans.