I will almost certainly vote Lib Dem. I live in a Labour-Lib Dem swing seat, as our former MP (before 2015) was Liberal and was then replaced by a Labour one. The old MP did a bunch of really excellent stuff for my constituency - he got the competition commission involved in breaking up a deal that would've been bad for my town, he secured more funding for schools in the area, and in general you often see him around living his life here. He's approachable, intelligent, and dedicated to the community.
Unfortunately his Labour replacement has been completely crap. He's done absolutely nothing since the last election and is a general nonentity who doesn't seem to care about the area at all. He's also making no effort to win the seat even though his majority is tiny, which smacks of total arrogance to me. Much as I'd prefer Labour to win the election, unfortunately I just can't really donate them my vote when their candidate here is so bad.