I am a minnow and I upvote anything and everything that I think deserves it. I have been on Steemit for three weeks to the day, and have a meagre 80.725 SP.
I have to admit I have held back from voting on a few occasions when my vote power has been down to about 54%, so 100% votes have definitely prevented me from upvoting content that I really would have liked to vote for in the past.
For that reason giving the slider at a lower vest level would certainly be helpful.