We spent 2 nights in Glasgow in April 2007. We found the museums / art galleries excellent but the rest of the city either so-so or ugly. The so-so parts are around Mechants City, but being as generous as I can there is not much else to engage a visitor unless you want to visit chain stores available in all big cities. One overall factor is that everything occurs off the streets, inside renovated buildings or malls, leaving the streets themselves feeling bare. In addition, practically every doorway, litter bin, corner etc is made the focus of communal vomiting and urinating by nocturnal drunks. I appreciate this is costly to keep removing but c'mon!
There is an excellent public transport infrastructure, which seems not to be explained well, and bus drivers seemed especially surly. There is also a city sightseeing bus which is well run but to be honest the 'sights' didn't grip, and our tour guide started extolling the virtues of Edinburgh!
For the cost, you would be better off getting public transport directly to key venues.
Overall I would recommend a day visit to Glasgow but not more.