I have a number of customer now using it basically because they got sick of paying massive amounts of money to Microsheeeite ever few years on upgrades. Did an install over christmas, Ubuntu Server and 20 Ubuntu workstations and its working a treat with open office. All their other software is web based so i'm busy going through it now and tidying it up to work properly with firefox as it was originally wrote to work with IE (not by me I hasten to add)
Its amazing how quickly people want to move away from Microsoft when you give them the option of keeping their current machines and addint Ubuntu or spending a small fortune to upgrade to Windows 7! Biggest hurdle for me was staff, who seem to have the attitude of "well windows was better because..... <substitute some stupid comment here>". Each OS has its merits but for a Free OS, Ubuntu is great.