To follow up for anyone else who might be looking for an English translation of Sappho:
I've now read Carson's If Not, Winter; several times in fact. I can't speak to the quality of the translation as I don't read Ancient Greek, but I found it an extremely enjoyable experience. For those who do read Ancient Greek, the book presents the Greek on the left with Carson's translations on the right.
The language is simple, yet evocative and Carson has made the fragmentary nature of Sappho's poems into a positive. The brackets noting missing parts, in translation, actually add to the poems structure as do the blank spaces on the page.
One of my complains about Poochigian's version (or at least the abridged version I had) was that it wasn't always clear when a new fragment started or if it was just a new stanza in a longer piece. There's none of that confusion in Carson's edition.
There are also some differences in how the two translators decided how to structure their poems: Carson's don't have end rhymes and the way thoughts are continued from one line to the next give the poems a rhythm (Carson says she kept the word order the same as Sappho's Greek). Poochigian on the other hand uses end rhyme and seems to have imposed a sort of traditional English poem structure onto the poems. Poochigian's version isn't horrible, just not to my taste. I'll post an excerpt from both so that everyone can get a taste of the two, because tastes are different.
Carson's version also has a good introduction where she explains her intentions as a translator and there are notes for many of the fragments in the back that point out why she made a particular choice over another or to give you some background on where the fragment came from. For an in-depth scholar, these notes won't be enough, but I found them very interesting and informative. Or you can choose to just sit back and enjoy the poems on their own. Penguin books also usually have good introductions and notes. Mine didn't, but I'd be surprised if the unabbridged edition didn't.
Just FYI: In 2012, a new Sappho fragment was discovered and so Carson's If Not, Winter is no longer a complete Sappho collection. It looks like the Cambridge edition is the most complete as of now.