I use Avanti to get from Carlisle to Euston every week, or every other week, depending, and I thought I would give Lumo a go for one trip (last week).
The bad:
Decor inside of the carriage seemed quite dated compared to the Avanti Pendolinos.
The windows were all streaked with a rusty red substance or coating that looked like it was peeling off.
There was no 'Lumo Eats' trolley on the train - Announced it wouldn't be available.
The journey took 20 mins more than Avanti (but I knew that when I booked)
It only reached a maximum of 110mph (Why so slow?)
Worse than the above was that I suddenly realised that if there is a cancelation or a major delay with my Lumo, or more specifically, the last one out of Euston at 16:36 then I'm totally screwed. Can't get home. At least when there is a delay or cancellation with Avanti I can just jump on an earlier one or a slightly later one, no questions asked, as there are so many running that route daily. I do this regularly. If I see issues on the WCML, I go to the station early and jump on the first Avanti that arrives.
The good:
The carriage was larger and more airy than a Pendolino. Big windows were nice.
The toilets were more roomy than a Pendolino, and they didn't stink anywhere near as bad as an Avanti train.
It was £15 cheaper than Avanti for the return trip.
All in all, I think I may stick to using Avanti, sadly.
For a £15 saving for the return trip, it simply isn't worth the longer journey times, the more inconvenient and infrequent trains per day (only 4 Lumo per day vs 28 Avanti), and the risk of not being able to simply grab an the next one in half an hour (or earlier) if there is an issue.
Bit of a shame. Was really looking forward to having an alternative, but I guess I should have realised all of the above if I read into it more.