The max speed of a Pendolino isn't 125 -
http://en.wikipedia.org/wiki/Class_390
"The new trains were intended to run at 140 mph (225 km/h), but the West Coast Main Line modernisation programme, which was an upgrade to the infrastructure to allow faster line speeds, ran over budget. Consequently plans were scaled back, and in a manner reminiscent of the introduction of the Intercity 225, the lack of signalling upgrades resulted in the maximum line speed being restricted to 125 mph (200 km/h). "
You can't blame the train for not going fast enough or Virgin for only achieving a 15mph speed improvement - the root cause is Railtrack / NRs responsibility.
I've used the Pendos a few times and they're absolutely fine.
Priority should be given to seating over luggage - sorry the train is there to transport the person as the first priority. It's why FGW are right to have configured some of their HSTs with the airline style seats - to minimise the number of people who end up standing.
I've never had an issue with the view out of a Pendo. If I get a seat without a window view, then I sit and read, it's not a problem.
The seats on Pendos, Voyagers, Meridians and Desiros are, for me, much much better than what preceded them - as I was reminded when I got an HST on the MML the other day rather than a Meridian.