I never really took much time to comment on the Slim after receiving it so I guess I can add a few pics and thoughts.
I have been using my Slim almost daily for a few months now. I primarily use it for the commute with the Nano and on flights. I have also found that pairing it with the Pico DAC out of the computer or iPad makes a fantastic little desktop system.
My main listening sessions are the 45 minutes to and from work with a Nano full of AIFF music, Whiplash LOD, Slim and either JH13s or UE11s.
I have historically had a lot of trouble with portable amps during this commute in a very rich RF environment. The amps ranged from unusable to periodically annoying. The Slim has zero of the stray RF problems. I have on rare occasions gotten the cellular chatter when receiving an e-mail on the BB right next to the amp. As far as portable amps go this one provides the most interference rejection which makes it a winner in my book right out of the box.
I have heard most of the big name portables currently on the market and certainly have my favorites. I used to own the ALO Rx and thought it sounded very good, in a few areas just as good or better than the Slim. Overall I prefer the sound quality of the Slim and the better volume control and its much greater RF Rejection made it a clear winner so the Rx is gone.
I have also used the Slim a bit in my home office with the ATH ESW9s as they make a nice little package. The AT go well straight out of an iPod/iPad so there is not really a dramatic upgrade in sound quality when they are amped. I typically notice problems with amps through these more than obvious upgrades to the sound. When comparing to straight out of the iPod I primarily notice tighter bass and maybe a bit more texture in vocals and strings.
I really like the Slim in my portable set up but think it really shines when connected to the Pico DAC. This combo is very, very good in my opinion and has become my constant travel companion. Such a small package that can outdo much larger systems that I have heard.
Out of either the iPad or the big computers this combination seems to really gel and makes some fantastic music. I find that the better you feed the Slim it just keeps getting better. While I preferred the new JH Audio JH-3A, which sounded fantastic, I am not going crazy waiting for mine as I am perfectly happy with the Slim and the plain old JH-13s.