I've also taken advantage of the flash sale - 2 months' 1st Class for my wife and I, reflecting our newly retired status.
We're experienced Interrailers, most recently in 2018.
However this is the first time with mobile passes - we preferred paper but couldn't commit to dates in time for the offer.
It would be great to hear how others get on with mobile passes.  We're reasonably 'digital-savvy' but never too proud to accept tips, recommendations or just stating the obvious!

Does anyone have any experience with this Rover / Ranger product, in particular which bus services are included?
The GWR^▸ (Great Western Railway) website has a link for bus services that refers you to Cotswold AONB^▸ (Areas Of Natural Beauty).
This Cotswold AONB website states 'Please contact Johnson’s (sic) and Stagecoach directly to find out which routes the Discoverer Pass may be used on', although doesn't give any contact details.
On calling Stagecoach West at Gloucester, I was advised to contact GWR. Johnsons don't appear to answer their phone.  And GWR at Gloucester didn't know.
Any help appreciated.

How about TfW 67's and Mk4 stock?

Cardiff - Holyhead loco-hauled not resuming until 13th September according to North Wales Coast [http://www.nwrail.org.uk/nwnews.htm]

Short sets but they have buffet/restaurant facilities  

Just a thought...

Hit the post at Valley Parade

With Chiltern's Class 121's now surplus to requirement, one should be enough for a footex from St James Park

Indeed - but not with a seat reservation (I believe)

Today I attempted to purchase a first class ticket for the 08.54 Bath Spa to Plymouth on Saturday 23rd April (1C04).
First I tried a station booking office and was advised 'sold out'.  And that's sold out on all tickets not just First Advance.
That's never happened to me before, even after the reduction to 1.5 coaches - so I tried on-line only to get 'Service FGW^▸ (First Great Western) 1120 is closed' (11.20 being arrival at PLY^» (Plymouth - next trains)).
A one off ?  Or is this now a regular occurrence ?

realtime trains is showing two late services from Paddington to Cardiff via Kemble on Saturday
23.30 IC36
23.59 1Z37
 

Noting Mr Red Squirrel's musical taste, perhaps 'Close to the Edge' is rather appropriate?

An interesting route, noted at Realtime Trains, 1A91 16.03 Plymouth - Paddington.

SSux 5th January - 3rd April 2015

Does anyone know the reason?

There is a seating map for Coach L on thetrainline.com

Although only 7 of the 15 airline seats have numbers.

Does this indicate that reservations will be restricted?

Hopefully the 07.06 will run via Bristol instead of the 07.30 - but noting the journey time, I doubt it. 
Otherwise, not too helpful for me - a long time user of the 07.30 ex-Paddington, travelling from Chippenham direct to Plymouth.  I believe the only direct train of the day, in this direction.
Linked with the withdrawal of my favoured Coach G, it's going to be very tempting to take the car after December.