The problem that I have personally with NAT Group is that whilst their fares are reasonable in comparison with Cardiff Bus and Stagecoach, they seem to just have every hand-me down, in the way of ex-Metroline E400s (understandable as they're both a subsidiary of ComfortDelGro), ex-Stagecoach London OmniCities and ex-Arriva London Geminis. The only route which has a pretty much 100% guaranteed standard fleet is the X8 with the Optate Metrocities. The X1 has its branded Citaros (BG63 VVE/BF65 HTZ and BF67 WGY/Z/WHA-D), but older ex-Quality Line (BN12 EOP/R/Y/Z) Citaros regularly turn up. BF65 HTX was destroyed by fire two years ago.
Punctuality is also very hit and miss, and none of the local live time sites seem to pick them up.
The ex-X1 Metrocities (501-510, YJ15 AOL-V) are in use on wherever, with two of them still being branded for the X11 which was withdrawn in November.
They need to spend a little bit of time tidying up the Cinderella-style fleet at the moment before they do anything else.