When I was almost 59 I decided that it was time to learn to solder SMD's. It made perfect sense to wait that long. I can't see as well as I used to. My hands aren't as steady. But! I am grandkid trained. I have lots more patience (cough). I stopped aging when I turned 6D. I am now 6D2. The alphabet age is wonderful :)
When I finished my first (very simple) project I wrote a beginners guide to soldering SMD components and put a (somewhat tongue in cheek but not completely) post on the EEVBlog forum.
There were some pretty good additions and one flame war that I never did figure out what tripped their trigger, but I didn't try very hard either, in the responses.
I have a reflow oven that I bought off of eBay. It's fine for populating a group of boards but I rarely do that. Besides that, you have the added step of putting solder paste on the board. Solder paste expires, I never mastered using a stencil, and you still have to place the component by hand if you don't have the dinero or desire to own a pick and place machine. No more than I work with SMD I think hand soldering is fine. I can solder 0204 components with my microscope. That said, I don't "like" to solder 0204 components. I will sometimes use hot air and paste. Sometimes I use paste on one or two pins and the soldering iron to tack it in place. The paste seems to anchor the part in the spatial dimensions I can work in.
I read the discussion about Nano's, Arduino's, Microchip, etc. One of the common comments I see from Hans is how little room there is left for code changes. The Arduino bootloader uses some of the limited memory on the ATMega chip that he uses. That doesn't bother a no-talent coder like me, it makes it easier for me to blink an LED, but I think it would make the QCX, as we know it, unlikely to have come to be.
I defer to Han's experience with mass producing boards. I wouldn't mind doing the SMD soldering myself. At least I wouldn't as I type this. Check back with me after the last component flits off of my tweezers and flies off into whatever dimension Satan resides in :)