Is astrology important in lives of devotees?

To the degree a devotee is purely surrendered to the Lord astrology is not relevant in his life. After all, Krsna can modify the material nature in favor of the devotee any time as He demonstrated in protecting Arjuna.

But to the degree devotee still suffers under the modes of material nature, he may become interested what the cause of his suffering is. The influence of supernatural powers cannot be denied. The question if one is affected by that influence or not. History of human kind has plenty of examples how irrationally masses of humans can be controlled, how they enthusiastically reach out for their own destruction by the time the karmic clock is ringing. Like remote control sheep they march, following their empowered illusory leaders.

So, to be informed might be useful, but to be absorbed in astrology is detrimental as one more less denies that Krsna could be able to overrule His own design. Srila Prabhupada stressed and demonstrated on His own example that even His lifespan was stretched beyond death. While facing death He delivered the last lesson to His disciples that finally everything is totally in Krsna’s hands.

For grhastas, provided one finds a bonafide astrologer, which is not at all for sure, a horoscope serving the compatibility of the partners according to guna and karma might be of some use. But even here Srila Prabhupada said: "It will be all right when they are devotees". To be a devotee means finally to tolerate and by power of devotional service transcend astrology.