Great Western Coffee Shop

It just struck me now LONG that seems to take ... half an hour Highbridge to Weston?   Or have I just been mislead because of the psychology of it going from 14:xx to 15:xx to 16:xx to 17:xx?

No wonder people prefer the XC speed from Taunton to Temple Meads, and no wonder the people of Bridgwater would like to be able to get on!

2.5 hours Taunton to Cardiff.

The "fast" Bristol to Cardiff services (aka the ex Portsmouth services) are timetabled for 48 minutes at their fastest (tho still can do it faster due to padding in the timetable).
The slower services to Cardiff are generally given just over an hour (though some are just under).
The "fast" services between Taunton and Bristol are given 30 minutes (some are 31, but its close enough!).
The slower services are given just over an hour too.

All isn't as it seems though due to the connection at Bristol, so most journeys with the connection are given as somewhere between 1 hour 50 mins and 2 hours 8 minutes.
Given that that particular direct train seems like the slowest, and others are timetabled for between 2 hours 6 minutes and 2 hours 20 mins, depending on when you travel, taking the "slower" train may work out quicker!

Of course all that only applies if you are travelling west of Bristol towards South Wales and in that case you have the additional benefit of it being a through service, especially right now when changing to a new GWR service at Bristol seems like it can be a bit like rolling a dice when it comes to will it be on time or even be running at all. If you are just travelling to Bristol then the XC services are a no brainer at about half the journey time (unless you have literally just missed a fast one).

Haven't I seen a suggestion that the Castles may make it as far as Cardiff ... and also heard discussions about the need to add service from Bristol to Cardiff above the current two per hour?

A study of the possible suggests Tauton - Bridgwater - Temple Meads - Abbey Wood - Aztec West - Newport - Cardiff in about 85 minutes, allowing time at Temple Meads for massive passenger flows on and off the train and a crew change. Call it 89 minutes with a stop at Worle as well, or 95 with a stop at Weston-super-mare instead of Worle.  That's the possible on current stock type plans - not a business case, but I suspect hourly, coming up from beyond Exeter and connecting into a Manchester train at Temple Meads it might stack up.