Current IBMs have a good rep for reliability. Older IBMs had some driver issues with earlier versions of Windows (especially NT) because of non-standard video and audio components, but otherwise ok.
Dells have had a good rep, but the last two we got at the office had some QC problems (drives and keyboards, IIRC).
Old Fujitsu's were supposedly OEM'd by the same manufacturer as the Hitachi Visionbook series, and Hitachi's were good machines (I still use mine and it's 3+ years old). Don't know about new Fujitsu's.
Old Toshiba's were suck - husband used to work on them and swore he'd never have one in the house; he liked the old Compaqs. Seem to have switched places lately, though - new Compaqs are trouble, new Toshibas seem to be better. Wonder if they switched suppliers...
Lady Niniane