It's an odious passive-aggressive habit. "I love you, you always have so much to contribute" means, "I hate you, and wish you'd just shut up." or "I love you, you're always willing to step up!" means, "I hate you, and wish you'd just do what you're told."
The effect is to communicate anything but a loving feeling. And what's more, it undermines any future protestations of actual affection. Maybe you just can't take the Philly out of the boy, but I always preferred it if someone just admitted I was bugging them! I haven't gotten the "I love you" of death, myself, but I've heard it used at least two or three times a night, and it's never meant kindly. How fucked up is it that "I love you" is a nastier thing to say than "You drive me crazy!" It doesn't soften the blow, it doesn't negate the criticism, it just makes the utterer sound insincere. and mealy-mouthed for not just speaking the truth.
This is one of those verbal ticks I really don't like. It's even worse than lolcats.