Just to sharing that I already called Dell ProSupport regarding my issues with my Vostro 5470.
I bought the laptop last Saturday, and encountered multiple issues such as WiFi connection unstable, LCD dimmed when opening darken image, and power button that hard to pressed.
First call made at Monday evening, explains in details all diagnosis that I've done, and the tech reps (the girl one) asked for a few diagnoses that I missed-up. I made a second call at the night, 10pm, to report the result. The tech rep tells me that he will bring the cases tomorrow morning for further steps (for hardware preparation, technician appointment etc).
Next day, I called back, and since my cases registered at Tuesday, they can only assigned the on-site engineer at the next day, which is Wednesday. In the afternoon they called me back to confirm the appointment and get the details.
And on Wednesday (which is yesterday), I receive a call from the technician for confirmation on today's appointment, and although there's some issue at my ends, he comes at my home in time (actually one hour earlier than planned). Replicates all issues successfully with my assistance, and he replace all things that related (LCD screen, LCD cable, palm rest fullset including keyboard and buttons, WiFi etc). A very good person in my opinion and very details in getting the job done. I even helps him a few things, such as renew the paste, and exchanges some knowledge especially repairing this model, Vostro 5470. (I'm a software engineer myself, so there's a few things I teach him also

)
During that time, every parts of the laptop including LCD bezel and motherboard already opened up. Trust me, this laptop parts mechanism was very-very simple, compare to various laptop I knew before. Maybe because of the nature of ultrabook.
And the best thing is, although my laptop is already new, but most of the parts are already replaced with the new one that specifically QC'ed (quality checked), parts by parts.

For WiFi cases, I requested for Realtek brand, but it can't be done because of no stock available for short time (I can't wait till today as I want to return to hometown. I actually at the countryside as I type). I still got the same Intel 7260 one, but very difference in performance compare to previous one. I assume not all Intel wifi card are defect. But I will do another multiple round of test to make sure of this.
Overall, the service from Dell, just like everyone else said, was very good. Maybe because I got lucky to get the friendly one, but overall my encounter with multiple Dell staffs was positive.

I also have problem with my screen (cable), when i touch the bezel beside the dell logo the screen will blackout. Btw, how they manage to fix the autodim with darken image issue?