I'd agree completely with what sekio says above, and I consumed gallons of the stuff in the late nineties. It's largerly interchangeable interms of overall effects with GHB and GBL, but they are all palpably different and unique from one another in subtle yet distinguishable ways.
Again, sekio is correct when he mentions the higher potency and longer effects of 1,4-BD versus the others. But to distinguish it more from the others, subjectively I'd add that in my experience (though it's been awhile) the effect of 1,4-BD always tended to be of a slightly more inebriating quality--perhaps most evident in muscular response and overall physical coordination--than did that of GHB or GBL. At least until unconsciousness creeps up on you--then they are all equally incapacitating.
At any rate, this inebriation isn't "dirtier" (as sekio again remarks above) than the others I've tried, but I'd venture to suggest that it is perhaps a bit sloppier at times, if that makes sense.