Responding to a social media question: What are my favorite translations of [old/middle] Irish material?
I don't know that I necessarily have favorite translations, per se, so much as favorite translators. So if I have a choice I tend to look for work by Kuno Meyers or Elizabeth Gray when possible because they are two of my favorites. Meyers because he footnoted like nobody's business and he's very good about discussing alternate possible reads which I really appreciate. Gray because her work is newer and so incorporates newer understandings of the language. Macalister isn't bad and his work on the Lebor Gabala Erenn is valuable especially for the notes and appendices, but he tends to take the easiest English translation option rather than (in my opinion) what might be the most accurate. Dunn's Tain Bo Cuiligne is decent although like most translators especially of his period he tends to add material. I abhor Whitley Stokes and may never forgive him for his appalling treatment of the Cath Maige Tuired.
Whitley Stokes is actually the reason I started teaching myself old/middle Irish, so that I could read the Cath Maige Tuired for myself after I realized how much he was both adding in and editing out. And that sort of thing is exactly why you have to be very careful about translations especially of this material. Older Irish doesn't lend itself to literal translation to English because to an English speaker what is rendered tends to look clunky and redundant, however in altering the material to better suit an English language audience the feel and spirit of the original is, again in my opinion, often lost. What we are left with may seem beautiful in English but it may not reflect the original story, only the translator's opinion of the spirit of the original story and that quickly becomes perspective and opinion.
I highly recommend checking out University College Cork's Irish Sagas Online which includes side by side renderings of many important texts in the original older Irish, modern Irish, and English. For those seeking reasonably accurate versions of a selection of the stories Cross & Slover's 'Ancient Irish Tales' offers a fairly good, close to the original, version of many of the more popular stories.