Well since there is no stickied feedback thread, I'll use this one to post my thoughts.
I really liked the game to start off with. Keeping in mind that it was a development team of three people (all of whom, if I'm not mistaken have no programming experience) and I'm guessing a fairly small budget I have to say this exceeds the expectations I'd have for the game. I find it unfair when people compare it to Portal (aside: Ironically, if I were to say it's like any game I'd say it reminds me more of RUSH in first-person form) when Portal had a much bigger development team and a lot more money behind it. From what I see, a lot of people expect a story as good as Portal and complain about game time when in fact I found the campaign ran a bit longer than Portals (just without replayability--pending possible future DLC). This game delivers exactly what it promises, I think most people just expect Portal when they're buying it, however it's clearly stated on the Storefront:
"There's little to go on as the game begins - the player is dropped into an all-white room with few instructions, and simply has to figure their way out. The tone of game changes as the player finds small and big alterations to their environment, supported by an original score, inviting each player to let their imagination take over as to where they might be."
I really need to stop this rant, but let me just finish that no one rags on games like RUSH, EDGE, or Toki Tori because it has no story. There is absolutely no difference, except peoples expectations.
NOW that I got that out of my system, what makes QUBE great? I really like the ever evolving puzzle elements. I thought this was honestly the best thing about the game. Every sector offered new puzzles to figure out. Yeah it would have been nice to been able to explore each of the sectors a little longer and explore more difficult puzzles found in each, but again given what I know about what kind of production this was, I thought they did a good job of selecting some very good puzzles to showcase each sector. Also, I think it's worth to note that after reading through some of the threads on here, I've noticed everyone likes different sectors better, so they've done a good job of making them all fun rather than having one great sector with a lot of "filler" sectors. (Personally I liked the ones where you had to change the color of the balls).
Anyways, that all being said I'd definitely like to see this game expanded with some DLC and will gladly get it. I'd also like to see these developers continue making more games in the genre, hopefully with a slightly bigger team, more money, and some more experience under their belt. Hopefully they'll have the resources to make an even better game
Sorry for the longwindedness.