The Lowell Collected is a compromise between a standard trade-publisher Collected Poems--like the recent James Merrill Collected, which could be put together so quickly after Merrill's death because it's simply a lumping together of Merrill's published volumes under a single cover, with a few bonus tracks--and a scholarly edition that represents every poem written by a certain poet, with an editor who examines every version of every poem and attempts to create an authoritative text with copious notes. Both, in their own way, aim for neutrality--the former by a laissez-faire assumption that the poet's final published thoughts are definitive, the latter by working mightily to scrape away the errors of editing, publishing, and censorship that obscure the poet's true intent.
Lowell's Collected certainly took as long as a scholarly edition would--we've had to live with the Selected Poems nearly since Lowell's death three decades ago--but Bidart declares that he had "no wish to do a variorum, which tends to leave every variant at the same level of importance." Bidart is less editor or scholar than well-intentioned, meddling friend, declaring that he served as "both amanuensis and sounding board" during Lowell's lifetime--a characterization most reviewers have repeated uncritically, accepting that Bidart had superior access and hence should be trusted with superior judgment.
This is why I can't decide if Bidart is the best or worst editor Lowell could have--another poet, convinced of his own centrality in the Lowell universe, obsessed with his own role in editing, his own ego and judgment. Two of Bidart's characteristic tics--italics and repetition, stressing words that otherwise seem empty--are on display even in the first sentence: "Robert Lowell was above all an audacious maker--in poetry, one of the great makers of the twentieth century."