As a lowbie priest I find that I am very bad at managing aggro, when I get someone on me I tend to forget about the group and beat the snot out of this stupid mob...yes I am shadow spec, so it's best if you can keep the aggro OFF the priest, if I try to heal you while I am being beaten on it takes twice as long or more. If you need healing it's better to have no aggro on the priest, you may lose health faster but you will get a heal much faster then they can kill you. As for the always group with them I totaly agree, I always enjoy healing over killing anyday, it's easier and it's faster, those casts take much less mana. Aslo as for the other healer thing I totaly agree as well, a pally and a druid are both nice, but they are no replacement to a priest.
There is my input.