The first generation of Ultrabooks was rushed out. Everything felt unfinished. Not the Aspire S5. Even though Acer's last Ultrabook attempt, the S3, was very middle-of-the-pack, the S5 looks like it's going to be good. It feels absolutely nothing like the S3. Where the S3 was plasticy, and overall cheap-feeling, the S5 is heavy duty and complete.
The aluminium body is a little heavier than we're accustomed to in an Ultrabook, but that's a little bit because it's coming in at a larger size. The 13" screen seems to handle color better than the S3, which had the same resolution (1366x768)—though that might be a function of the super-dim room the hands-on models were in.
The keyboard and trackpad are also much improved. While the S3 was very, very functional, but felt cheap. The S5 retains that functionality, but now feels polished.
The power-open, magical IO-port-housing bay in the back of the S5 is very cool, but you can't help but wonder about durability. Also, it's a little like power-operated doors or curtains or anything: yeah, great, luxurious, but when I'm in a rush, I'm probably not going to want to wait for it to open to get at those ports.