Please have a look at this comparison. I wonder if I'm missing something or if Blender can't currently cast shadows within Material View in the viewport if I'm using Cycles. As you can see, on the right, shadows are cast on the side of the object that's not being hit by light. That's not happening with Cycles (on the left). This is using Material View. If I change to Render View, it shows them, so it is not a wrong setting (I mean, it's just the startup setting, just changed the Sun into another kind of lamp).
It's my first time getting into Cycles, but this is stopping me. And I have already searched everywhere for an answer and failed. I mean, I took the time to search well because I wouldn't think this could happen, but apparently nobody else in the web asked for this.
The point here is that I need to work using the Material View. It is faster for modeling and texturing. It's what I've always used within Blender Render. But that won't work with Cycles, and I don't want to use the Render View "live" because it is slow and the constant render destroys my CPU. Even if I switch to GPU the processes are high resource users and use a lot of RAM (not with a cube btw, this is just a quick test). My whole pc would be constantly busy with this only program and I don't get why, if until now, using Blender Render, I was able to do tons of stuff at the time without making my pc suffer because of Cycles. My pc's specs are not the problem: 16GB Ram /i7 8cores 2.5GHz /Geforce GT 650 2GB. Everything works here, of course a constant render doesn't properly, but I see no point in having a constant render unless I need it for feedback.
Here's the .blend file: