well it looks like for now Bungie doesn't mind what spills out during the open Beta. So many youtube and people writing about stuff.

It gives access to 2 PvE missions and 2 PvP modes (casual, competetive), max level characters of 20 and range of legenadry/exotic weapons via drops. The think I find the most interesting is that within one PvE mission there were optional time limited mini-bosses that dropped loot crates. Exploring the map it gave me the impression that Bungie will be reusing maps for missions and the somewhat hidden mini-bosses are going to be normal additions to these missions. The crates didn't unlock anything though. I found a rider-able flying motorcycle called a pike way off the beaten path as well.

I haven't really tried out PvP since in this Beta there is no training notes anywhere so you got to basically learn on the fly. I didn't know that a players loadout was the same for PvE as it is for casual PvP but the rules of damage is different. For example in PvE, slow firing revolvers are high damaging at any range and can be fired accurately from the hip while in PvP it's range is reduced and it's spread is increased for hip fire.

Also I'm playing with a kensington trackball and I needed to lower the sensitivity a lot and I'm still able to quickly track heads and get accurate shots in a moments notice. From what I read about consoles players of Destiny 1, aim assist was very valuable to them.
But it's clear for PC players it's pointless. Nice that it's off by default.

Though I come from playing Titanfall 2 and I feel so slow in PvP that I may not ever actually play that mode.