Well I cannot agree. The fillers were the only things I did not like in their animating (however, some of them got me interested), the whole rest was pretty good and satisfying, no unnecessary hundreds of blood.
Compare the OVA to the 2 seasons, the mood has changed completely - from an adventure and love to a sad, grim travels with a brutal events. I'm not sure if it is what people like in animes. Obviously I like to watch battles, but those do not have to contain such scenes like eye chowing (uhm, seriously this was loathsome :s). The way BeeTrain were doing satisfied me at all.
I might have forgotten some arguments againt BeeTrain cause the last time I read this forum was when I registered there, but I don't remember mentioning anything despite the fillers and the violence level. Are those the reasons why you think so?