I've done it a few times and it takes you to some remote places without throwing stupidly steep climbs at you. If you like real countryside you'll love this. Cow muck, red kites and cakes, though not all at the same time.
It starts off with a flatish run along the coast, giving you an early time buffer. Then into rolling countryside on very minor lanes. One or two steeper climbs before Llandovery, but fast easy bits in between. A mostly steady climb after Llandovery, then heading south towards home. The last miles are on busier road, so the least enjoyable. You don't need to be super fit for this ride.