In reply to phja:
I did the Northen half in March last year, Broad Haven to Cardigan. I Can reccomend Broad Haven to St David's, and the next few days. Takes in Newgale, Solva, the Blue Lagoon etc.
Fishguard to Cardigan I was a bit less impressed with, but might have been knackered by then.
South Pembs is prettier and north generally more rugged, the path was near enough deserted in March, saw the odd day walker but nobody through walking. Plenty of ascent and descent to contend with!