The Epic Universe thread had me thinking on how soon after a park opens have you visited?
For me, my first visit to Disney-MGM Studios was January of 1990, right after Star Tours opened. So it had the kinks worked out and still pretty fresh. Also my family visited Animal Kingdom June of 1998 so it was pretty fresh.
In contrast, my first visit to Universal Orlando was in 1992 well after the horror stories of the opening days had died down. It just comes up, do you want to be there right around opening or wait a bit for it to get better and over "growing pains?"
I waited 34 years for UO to work out the kinks :D
The downside is, I think I missed a lot of attractions I really would have liked!
Did IofA soon after it opened. Lots of fun but lots of headaches. I would prefer two years. Doubt I can wait that long for EU.
Given that Epic is opening officially in May with presumably plenty of soft opening for AP's, media, and others probably extending back into April, I anticipate the park to be able to work out most of the kinks by July since it will get stressed pretty hard between Memorial Day and 4th of July. I probably wouldn't hesitate booking something in August and feel like everything will be working and most of the kinks will have been worked out.
FWIW, I did a quick look at prices for the Grand Helios for a random 3-night stay mid-week in October, and was quoted $346, which is a pretty great price. However, it is pretty clear that the Signature Resort DOES NOT include the same Unlimited Universal Express perk for IOA and USF that you get at RPR, HRH, and PB since staying at RPR for the same period was quoted at $495. In fact, a Club Level room at the Grand Helios (includes lounge access with breakfast, snacks, and appetizers) was pretty much the same price as a standard room at RPR. For comparison, a room at Stella Nova/Terra Luna is being quoted at $221 for the same period (Endless Summer is $167), so guest are paying a premium for the exclusive park entrance and overall design features of the Grand Helios.
You definitely have to wait at least half a year to get the kinks worked out. Otherwise, the park will be ridden with technical difficulties.