Aesthetics
This level's looks are more for function than form. Immediately you're introduced to the instructive colour scheme, which clearly define the rules of the game. The targetting bullseye should ideally have had some kind of colour - I found it hard to see against some parts of the chamber, particularly when looking through grates. There were certainly no problems visually, but the chamber remained pretty spartan - then again this isn't your typical chamber. Observation rooms light the chamber and that's about it; the cool lights give it the standard clean, controlled feel. Some parts of the levels are darker and shadowed; here the blocks that you summon are far too bright and look out of place.
It'd be nice if the level was made of tiles that weren't the same size. I know you have to show the player a grid for placing their blocks, but it would help break up the monotony even if there was the occasional 64*64 tile. Red zones in particular strike me as somewhere you can spice things up a little.
Gameplay
Rather than thinking where to put portals, you end up thinking where to put portalable surfaces. An interesting way of looking at things! There were two 'aha' moments for me: "Oh, these blocks are portalable" and "Oh, I can fling myself like this". I discovered that you could block the laser fairly quickly; I was more surprised that the blocks exploded by themselves! After working through the chamber, there was the small matter of completing the course under time pressure to exit.
The single most frustrating thing is the 'controls'. The bullseye target lags behind your camera movements ever so slightly, and its motion is jerky. Even more frustratingly, about half the time it doesn't go where you point! The script doesn't seem to like aiming while pointing down, or on surfaces close to the player. I don't mean to moan - of course you're working to limitations - but it got in the way a few times throughout my playthrough.
Whatever your thoughts, it was fun to experiment with a new concept. I just wonder if the idea would extend easily to other puzzles, or is it more of a one-trick pony?
Difficulty
The map felt like an introductory level. "Here's a new puzzle element, it doesn't work on red stuff, go solve the test" it says, which is the right way of doing it. (That is, let the player work out how it works for themselves.) Dragging out the concept through further training wouldn't be worth it, as the concept is fairly straightforward. I'd say it was medium difficulty - you have to figure out how to use something new, and then how it works with portals. I think the map could have benefitted from a second puzzle, however, because it did feel like an introduction. Some kind of development of the concept would have been great.
Bugs and Mapping Details
Not much to say apart from the bullseye. I noticed that the portal control buttons trigger the other butons, so more than one button sound can be heard. Also I managed to get a block stuck under the floor, but I could right click to destroy it.