Guru devotion is very different from being attached to the Guru. Both are different things but can appear to be the same thing. Guru devotion is the process and the act of doing in according with the teacher's instructions and also to trust him completely in his instructions without second guessing him or doubting him. If we doubt the teacher's instructions in an arrogant manner, why would we follow a teacher in the first place? Its okay to ask due to lack of understanding, but to doubt outright is not a good thing. The crux of Guru devotion is trust: do we trust this person enough to follow his instructions through and through? and does the teacher trust us enough to pass on to us the most sacred practices to us? That dynamic relationship is called Samaya. This is what Guru devotion is. With Guru devotion, the student does everything and follows every instructions with the clear knowledge and motivations that the main motivation for us to do this is to practice the Dharma and not out of attachment to the Guru.
Being attached to the teacher is very different: people who are attached to the teacher will not be practicing Dharma. Instead, they would spend their time to gain the favor of the Guru and play politics to get near to the Guru and they are usually the ones that are rude and will not hesitate to harm other Dharma students to be physically closer to the teacher, or so what they think. Sometimes, when the teacher passes away or leaves, it really makes us think and reflect on what Guru devotion really is. Even those teachers who are very devoted to their teachers, such as Pabongkha Rinpoche, did not train under their old teacher in their present life. He did not become the student of Dagpo Rinpoche again this life. If it was out of attachment to the teacher he would go towards him...it is the qualifications of the teacher that we should be 'attached' to.
That's how i feel, anyway, about Guru devotion