I use a computer based analyzer (RME sound card + AudioTester software) for most measurements on cassette decks or cassettes, however I own for many years and maintain in a good working order a hardware analyzer - Amber Model 3501 Distortion and Noise Measuring System. There are times when this unit is indispensable. It has an excellent generator (-116dB distortion/noise) and an ability to notch the main frequency and display the residual only together with the signal ("MONITOR" outputs). If I work (as I've used to do a lot) on power amplifiers, this thing allows me to see in details the distortion behavior of an amplifier , especially pre-clip with a difficult/reactive load. I know of no other way to detect a mild oscillation (could be several MHz) in a particular part of the signal, showing exactly at what point this oscillation occurs. The same goes for crossover distortion. FFT analyzers give you a figure and a spectrum, however a good hardware analyzer gives you a proper window into the details of an amplifier behavior.
Cheers
Alex