The new tubes are nice. The JJ's sound really phat and warm, and the amp doesn't seem to be working quite as hard and no breakup, although they seem to not have the high end push the original Fender tubes from '77 had.
Another big plus is that I don`t get the shit shocked out of me anymore.
In case anybody wonders why it took me so long to change the tubes...
This amp sat in a storage building for over 20 years without being played through. I used Acoustic,and GK's for quite a few yrs before deciding to go back to tubes.