It's my first time to make a review so sorry if i'm not so thorough with my analysis. But here's my take on this.
First and foremost, this manga is not a yuri. Yes, the lead characters being all girls may be misleading but i assure you it's not yuri. Love lab is about Student council members of a prim all girl's middle school studying about love and along the way, trying them out with their limited male acquaintances aka love interests. In the most hilarious way. In a way, i find the plot to be plausible and the story progresses rather nicely.
art is pretty good. The chibi look of the characters actually suits the cute, comic storyline and you could easily tell whose who because they look substantially different. It would have been 10 if Yan-san look not like a background character.
I love all the characters. Each one have their own individual characteristics and antics that makes the story so much more funny and entertaining.
It never fails to make me laugh. Especially the poop prince picture part. I hope y'all get to read that. And i love the romance that blossoms as the story goes on. Kilig much!!
So overall, i give it a 9.5 rating. If you want an innocent shoujo-type manga that could give you a good laugh and not bore you to tears, then you should try Renai Lab.