Logged in on release day, had a few unsuccessful attempts at upgrading to Serum 2 when including a tip of a few dollars for this mind-blowing upgrade which you could easily have charged for. No doubt the server bandwidth demand was particularly intense on release day. I finally succeeded in upgrading by including no tip. What a shame that that was what enabled the transaction to go through.
I see now that the unsuccessful transaction with the tip is still in my cart. So I guess I can now offer a sincerely-felt and much-deserved thank you for this absolutely kick-ass release. I will now do so and encourage others who had similar experiences to mine to offer a voluntary tip now that it's easier for it to work.
Can I also suggest to Steve adding a tip button to the product page permanently so people can later decide to show gratitude.