Everyone on this site that has tried them loves them. I recently retubed my Traynor YCV40 with eurotubes, and, while I wouldn't say that my amp sounds 100% different, it does sound much better (i.e. cleaner seems less piercing, and the dirty channel has more bite and sounds a bit fatter and tighter).
Do a forum search on "eurotubes" and you'll have some good readin, I'm sure.
... and that's all I have to say about that.
[U]ALL[/U] generalizations are [U]WRONG[/U]
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[U]ALL[/U] generalizations are [U]WRONG[/U]
[/sarcasm]