What model is preferable nowadays? There are not lots of shops to test them at least in Berlin. I want 13" and lightweight, but still powerful enough laptop. Lots of ram, i7 CPU and a SSD disk. The most important thing is an excellent keyboard and touchpad. I heard Lenovo is not using the old and excellent keyboard in their laptops anymore and I haven't tested the new one yet.
So, no, the current t520 is not as well engineered as those old ones, but it's still better than the vast majority of its peers. And you get some great deals on refurbs and open boxes on outlet.lenovo.com.
Current MBA is only 4gb ram. That's a deal breaker for me.
My worry is that they've moved the page/up down keys quite illogically down next to the arrow keys. It just doesn't map right mentally - moving pages up/down shouldn't have to involve clicking keys either side of the arrow keys:
http://allthingsd.com/files/2012/05/Lenovo_tablet_X230t_stan...
Not too happy about the home/end keys for similar reasons.
Making the keys more ergonomic is fine but it seems there really was no incentive for them to change the layout to a 6-row one other than arbitrary stylistic reasons.
That all said, it's probably still the best notebook keyboard on the market. I have a MacBook here and feel/tactility of the keys is superior on my old 2010 ThinkPad (if only just - they're both great keyboards) - on the new models, layout issues asides, it's supposed to be even better.
No product out there at the moment that gets everything right. The MacBook Air probably comes closest, although the battery life and TN+ display could both be substantially improved.
Note that the ThinkPad X220/X230 has both a better, IPS, display and can run for 12+ hours using a 9-cell battery whilst still weighing less than a 13" MacBook Pro. However, it's heavier than the newer slimmer notebooks and has lower resolution:
http://blog.laptopmag.com/record-breaker-lenovo-thinkpad-x22...
One of the nice things about it was that the volume / brightness hotkeys were hooked into the BIOS so I could use them even when the OS was locked. I believe all ThinkPads are like this. I miss this on my current laptop.