Now, after the update, I went to try the changes on a 32 player Dustbowl server. I primarily main Heavy/Medic, but I go Demo at times too when I feel that it will benefit the team, though not as often as the Engineer and sometimes, the Scout.
Honestly, I did not feel any major changes in the ramp-up on the miniguns. I was as good as killing as before the update. The (australium*) sticky launcher felt similar too, although it did result in a few missed kills due to the ramp up. Note that before playing, I was aware the both the sticky launcher and the miniguns had this effect added.
Now, I am more of a casual player, though people have been asking me to participate in tournaments. I don't play Demo as much, so this doesn't affect me much, nor did the Heavy nerf affect me as much, possibly due to my playstyle.
My only advice is this;
Try to get used to the ramp up. Once you get a feel for it, you may do just as well as you did before the update. Or use the Scottish Resistance. The longer arm time means you'll get more damage out of them.
[list] It may also be best to see if a console command/server mod is created that disables the ramp-up.
Now, I don't main Demo, nor do I play 6v6 or Highlander, but I know how this feels. Hopefully, either Valve tweaks this so that it doesn't cripple the Demo as much or the community finds ways to take advantage of the ramp-up. The TF2 community is capable of some truly amazing things, so I have no doubt that we'll find new ways to play with this weapon.
* Yeah, I had to put that in. :P