We just stayed at the Conrad April 5-10, and it was a nice stay but even the Conrad still feels new and growing into its skin.
We used the free bikes to bike all around the Hilton property (they're connected by some small service roads) and while it definitely didn't look ready to open, they were working hard to install landscaping etc. Seemed the buildings and bigger stuff is mostly done.
I would delay a trip if your main goal is ocean swimming, since Tulum this year has one of its worst seaweed seasons in memory (according to locals). The mounds of washed-up seaweed are at least a foot high and 3 feet deep on places where it's not being cleaned constantly. We enjoyed sitting poolside and beachside and some short swims, once you're away from the shore the seaweed is ok but still not great. The Conrad had a team of 6 guys working dawn till dusk with wheelbarrows, shovels, and on some days pickup trucks and a huge dump truck(!) that made trip after trip after trip taking seaweed away, and each day there was more. We were told the seaweed is even worse at Playa del Carmen so it's not a Conrad/Hilton issue.
The area is a gated community so no vendors or anyone else, meaning it's a very quiet and high-end feel on the water.
I think that Hilton guests will have access to paid meals at the Conrad, and maybe (?) pools. The Conrad gym is fantastic. Conrad breakfast is in the top 10% of hotel breakfasts I've ever had, free as a Diamond on an award stay.
PM me with any more questions.