My Vizsla is like that when playing to and as you say Vizslaaustralia, when he was little it didn't seem bad at all. Now he's 10 months old, it sometimes comes across as threatening - however, it seems more threatening to the owners than to the dogs. I'm certainly no expert but I tend to go along with the belief that if it really gets out of hand, the other dog will let my dog know and tell him off (which is what he needs). And in some cases you just have to remove him if the owner and/or dog is anxious.
I guess that's no a lot of help but at least you know that you're not the only one. Does yours still do the same now? Mine is beginning to modify his behaviour to suit the dog he encounters so he's starting to read them better and figure out which dogs are up for it and which aren't. Perhaps that's maturity?