I hate my best friend's new boyfriend.... help!!!

Okay, ladies — pretty sure I'm not the only person who has been in this position. My best friend, who has been my righthand (wo)man since literally middle school, is beautiful, smart, insanely accomplished in her career, probably the funniest person I know — and has HORRIBLE taste in men. I'm talking the kind of taste that makes Elizabeth Taylor look highly selective. For years now, she's gone for total duds — who are not on her level, in any stretch of the imagination!! — and invariably, they break her heart, she cries on my shoulder, and I help her get back on her feet, only for the EXACT SAME situation to occur months later....! Most recently, after a particularly bad breakup in the spring, she asked me to meet this "new guy she's super excited about." I met him. And the thing is, it's not that he's done anything wrong (yet)..... but I can just tell it's a bad match. Same old pattern. And I am SO TIRED of going through the same thing with her over and over again. So! What do I do here...? Should I tell her how I feel, and risk ruining her current happiness for her (and my) longterm benefit? HELP!