As an aside just come back from Italy where I did fair bit of rail travel. Impressions of stations over there - some lovely station architecture, concourse and platform level generally v pleasant but some quite depressing subways to navigate to reach platforms (think more darker concretey versions of Stratford) and some stations seemed overly large for number of trains calling there.
Back to UK, definitely got to vote for Euston - find the lack of seating and the mad rush needlessly stressful, especially when travelling with luggage and/or kids. Its also v gloomy, and since the refurb works at nearby St Pancras and Kings Cross it compares badly to both now. Also had the misfortune of encountering a mouse merrily munching through some chocolate on a shelf in one of the station retail units a few years ago - when I reported it to a member of staff he seemed pretty casual about it!
Man Piccadilly - platform 13 & 14 have always been a mess, though I'm glad I've not had misfortune of experiencing the new arrangement folks on here have mentioned. The main station though is pleasant and far nicer than it used to be back in the early 90s.
Crewe - is slightly depressing but reasonably functional. Agree that Chester can be bleak - when changing onto a North Wales bound train they also have an annoying tendency of changing the platform at last moment, adding further to the anxiety of trying to get onto a rammed 2 carriage Holyhead-bound train.