Great Western's website has separate lists of pdf timetables for pre- and post-12th April; in the three that I've looked at (without doing a detailed comparison), the only major change appears to be that the North Downs line goes back to 2 tph on Saturdays (1 tph to Gatwick), while weekdays off-peak remain mostly hourly, with few to Gatwick. Reading-Basingstoke doesn't appear to have changed much, and for the Thames/Cherwell Valley stoppers you get the same pdf, with times from 25th Jan, in both lists.
However, NRE shows half-hourly stoppers between Didcot and Reading on Sat. 1st May; does anyone know whether this indicates an actual planned change, or just that someone has forgotten to take the other trains out of the system?
The pdfs on South Western's website have commencement dates ranging from 13th December to 8th March, so it appears that nothing has changed this week.