The new biostar lacks downvote from the beginning. However, I think a system with upvote only is fundamentally crippled. An upvote-only system encourages popularity but not correctness. Without downvote, the most voted question/answer is the most popular but may not be the best. We need downvote to balance the effect a little bit.
Several of users have proposed some minor modifications to downvote, such as greater penalty for a downvote, not displaying negative vote, only enabling downvote for users with enough reputations and displaying both numbers of upvotes/downvotes (in SO, you need 1000 reputation to see both numbers). I know downvote sometimes has side-effects, but we should not get rid of it without valuing its advantages.
PS: I prefer not to poll on BioStar features. Each vote is associated with a different weight. A user familiar with SO/SE is more likely to have a comprehensive view on a BioStar feature than a new user. His/her opinions should be valued more. One may argue weight-associated voting also happens to common answers. That is true, but in that case, accepting a suboptimal answer only affects a tiny fraction of users who care about the question; others can still see all the answers anyway. On BioStar features, however, a wrong decision affects all users and users have no choice. Seeking the consensus among experienced users is a better approach than poll.