I did a return journey from London Paddington Swindon today, firstly Platforms 1&2 at Paddington are still wireless, the work on the new roof, which is nearly complete, might be holding this up.
All the below is for the relief lines only as I could not see the fast lines, from Airport Junction to just east of Maidenhead I would say that 95% of the masts are up, of which about 90% of these have the boom fitted with about 90% have the support arms installed, on this section there is only one piece of new wiring installed since my last run on this line in February this year which is on the up relief just west of Iver, this is a short run and looks a bit of a bodge!
From Maidenhead to Twyford about 30-35% of the steel sticks are up and I guess nearly all the piles are in. From Twyford to Reading about 80-85% of the piles are in including most of the Sonning Cutting.
The wiring from just west of Tilehurst is detailed in the above post but the up relief wiring goes very close to the electrification depot just east of Didcot.
I did notice that there are no masts installed on the avoiding lines at Didcot at present.
In a previous post there was talk of a target date of Didcot to Tilehurst going live in very late May, no chance, there is a lot to do in the Didcot area, plus the gaps above.

Does anybody know if the test section includes Tilehurst to Reading depot?
From Didcot to where the four track section ends I would say about 35% of the masts are up and onto Swindon about 70% of the piles are in.
So give it another 4-6 weeks and we will probably see the test section from Tilehurst to Didcot finished and I would expect the Airport Junction to Maidenhead bit to see a lot more wiring very soon.