I wasn't sure if I should rate the actual Tain story or the Kinsella translation, so I went for the actual story. Kinsella's translation is very readable for the most part, but I do have one or two issues with it. 
 In terms of the Tain itself, I've struggled through parts of the original Middle and Old Irish as best I can and read translations ranging from clunky century-old trials to Carson's 2007 attempt. Why? Because it's just that good, in my opinion. I only discovered the actual texts a year or two ago (I thought the Ulster Cycle was just sort of passed down stories), and my mind was blown that I never learned about it in school or anything. People compare it to the Greek stuff all the time, but there really is no comparison because they're just too different. The Iliad is very obviously full of morals and poetry; the Tain is very obviously full of grey areas and humour. I'd compare the Tain to Pulp Fiction quicker than the Iliad. The 'morals' are there, but subtly hidden under the savagery, ala George RR Martin. And Cuchulainn is just great; the perfect example of the hazard-to-himself prodigy. There is no better sociopath than Medb, no better manipulative king than Conchobar, and no better grow-up-man! guy than Fergus. It boggles my mind that the version we have now was written down a thousand years ago. The only unfortunate thing is that the Tain is better when read in conjunction with the other Ulster Cycle stories (otherwise it's like reading one chapter out of a book). For example, you miss out on the complex relationship between Cuchulainn and Emer. As for criticisms, there are those those tedious passages of names and adjectives that were meant to be read out in rhythm or memorised as a show of skill, but I just skip them. 
 Which brings me to Kinsella's translation. It's very good for the most part, both the prose and poetry. He opted to keep to the original meaning more than metre for the poetry, which I think was the best move. He does a beautiful translation of Deirdre's lament for Naoise. But I do have two issues. The first and most major is that, though I'm glad he included some of the other UC stories before the Tain, he butchers some of them with no in-text acknowledgement. He does this a little with the story of Macha, and most glaringly with Cuchulainn's courtship of Emer. For example, the bit that he condenses to, "Then they spoke together in riddles," is actually a long section of the two of them testing each other's intelligence and deciding they're worthy of each other. Instead Kinsella's translation literally goes from 'hi' to 'I'd like to put my penis on you'. Classy, Cuchulainn. 
 My second issue is more pernickety and probably not surprising considering this translation was done in the sixties, but he does seem to alter the text to make it seem less like Cuchulainn and Ferdia were lovers. He doesn't go as far as he could and it's still pretty obvious, but take the passage where it says, 
 "Fast friends, forest companions 
 we made one bed and slept one sleep 
 in foreign lands after the fray..." 
 This is more accurately translated as: 
 "We were companions of the heart, 
 we were forest comrades, 
 we were men who shared a bed [lit. men 'togetherbed'], 
 back when we shared heavy sleep, 
 after hard fighting, 
 in many strange lands..." 
 The difference is subtle, but there, and there's a couple of other examples where he chooses words like 'friendship' where a stronger word was intended. Maybe he was just trying to keep the nature of their relationship more ambiguous till after the fight, or maybe I'm being overly sensitive on behalf of bisexuals in ancient literature and he wasn't trying to hide anything at all. But still, the sixties.