Hi Mike, I've fished it a bit recently, currently it's in flood and highly coloured, visibility down to a couple of inches. It had a good flush (an appropriate term for the Taff unfortunately) several weeks back and no ill effects noticeable in the Cardiff area.
The Saturday before last I Czech nymphed it and had a good mixed bag of chub grayling and trout, all under a pound on a very bright sunny day in very low water.
Fished it as the river was rising and coloured at the end of last week, had a couple of trout and grayling, all about three quarters of a pound + a few smaller ones in about two hours. Nothing amazing.
The larger grayling may be more switched on after this flood clears, I'll be trying for a salmon when it drops a bit, tomorrow or Wednesday probably.
I'm generally fishing Taff's Well and Radyr but the grayling fishing is very good below Blackweir at the moment, - it's just a bit too busy with passers by in the day, try a very early start.
Taff season with Glam Anglers & co. still only £30, includes some outstanding barbel fishing , plus roach, chub, dace, mullet and carp below Blackweir, the best mixed fishery that I know. Try fishing free lined bread flake there one day, it's a kind of lottery!