Yeah I bought it earlier as I have been watching this closely for years now. Full release is Friday 6th June. I played the Steam early access beta (levels 1-6 only so 14 new levels = 20 levels in the full version) which is 25% cheaper @ £9.99 until 5th June. Its a very solid game & amazing work considering only 1 man made almost the entire game over 3 years
For £9.99 I think its well worth it as the sense of isolation on the alien planet has a terrific atmosphere & there is a level where you have to walk over a very high canyon which has no checkpoints so you fall its instant death & backtracking to try again. I used a 360 wireless gamepad the controls are excellent & very responsive but it supports full keyboard remapping.
The gfx are also excellent outside on the planet surface it uses highres textures & looks nice but the interiors look dated. This game is more about gameplay/atmosphere than gfx though.
I can tell only 1 person made it as there is not a great amount of gameplay apart from the simple puzzles & jumping or pushing objects a little.
It reminds me a great deal of Commodore 64 games from the 1980's which had limited gameplay but great atmosphere & decent gfx.
If you like retro games with basic gfx (they are DX9 & could easily be DX8 as no fancy shader FX its a basic artstyle with little shader FX lighting used in the first 6 levels anyway) you will like this game & still its amazing 1 person could dedicate 3 years of his life to this & will probably only break even financially.
It deserves support not sure its worth more than £9.99 though (price goes up to £13.99 on release day) as there is not much replay value either so its short & sweet but while it lasts the urge to complete it & explore/find out what happened is very strong.
Its a basic mixture of an old Lucasarts PS2 game called RTX Red Rock & another Lucasarts PC game called The Dig.
For £9.99 I think you will easily get your moneys worth just don't expect more than 6-7 hours worth of playtime.