I got an HP6050A from ebay a couple of years back and have 60501B (150W 60V), 60502B(300W 60V) and 60503B (250W 240V) modules to go with it.
Used it a fair bit for PSU testing including response to fast transient current loads and for developing inrush limiting circuitry to put ahead of DC-DC converters in 28VDC avionic applications.
I'm happy with it and have had no issues, like much of what's on ebay if you can wait a bit, usually you can get things at a good price. I got everything for less than half the 'typical' price.
It's worst point is that it dates from HP's non-backlit-LCD era so the display is a bit poor but I tend to use it under GPIB control rather than via the front panel anyway because
a) It's mounted at the bottom of a rack and as one gets older the ground gets further away of course, so it takes longer to get down and press the buttons
b) Some of the functions can only really be accessed through that interface and
c) Having produced a couple of little scripts it's actually quicker to set things up that way. Ditto things like HP system PSUs and so on.