Bokura ga Ita interested me because I was bored. I rarely watch these kinds of romance-y animes, but recently I've grown fond of them since they tend to be short (20-30 episodes), cute, and funny. However, I feel Bokura ga Ita could have been finished out in 12-15 episodes.
The animation I thought was cute, though they use the same old bubbly, starry backgrounds repeatedly. Also, they tend to use flashbacks A LOT, and this got really old fast. I want to see new scenes, not the same old animation from 3 minutes ago.
The music... this really needed improvement. They used the same songs and sounds every episode. There is a chime sound they used during serious moments that got annoying really fast considering they used it so much in one episode.
Now for the characters.... this part here is why I feel the anime was ruined after 15 episodes. Takahashi started out fine, she was strong and cute. By the end, though, I felt she was nothing more than an annoying blob of tears crying at everything. She cried so much going into the final episodes I felt like I stopped understanding the anime because I didn't see what was so sad/upsetting.
Yano... I felt like he was never really in love with Takahashi to begin with. He was cute and funny, and a bit arrogant. However, by the middle of the anime all I felt from him was that he wanted a replacement for Nana and would never get over her. I ended up hating him more and more and actually did not want him to be around Takahashi.
Probably the only characters I consistantly loved and hated were Take and Yamamoto. Take's character was pretty much the same throughout the anime, and I thought he was quite loveable. Yamamoto, though I hated her, also was the same throughout the anime. I think it would have been a little nice to have seen her mature a little near the end and stop being around Yano. Her relationship with him just never really made sense anyways.
Overall I feel I would have enjoyed this anime more had it had ended earlier. I never felt like Yano and Takahashi were really a couple. It was almost like they forced them to hang out because that's what people want. Her relationship with Take is much more cuter. The only reason I'd recommend anyone else watching this is if you're really bored and wanting to get your mind off things. Even then you might just get sucked in and get bored with it, but want to finish it because you want to know what happens.