I usually assemble first prototypes of new board by hand as there tends to be errors on them and it's better to catch them before all the planned components are on board. Not all design mistakes are fatal (like having pull-up at one place and pull-down at another fighting, resulting funny behavior) but some are - like power module putting out 6,6v instead of 3,3v. So I prefer to be cautious.
Mostly hand assembly isn't that bad, even 0,5mm TQFPs are fairly easy to mount, but some components are just pain in the behind.
Like BGAs, or this one:
For reference, three footprints around there are 0603-sized resistors and capacitors. The component itself is only 2x2mm in size, and pads are just 0,25mm! (it's an accelerometer, by the way, and no, it's not available in more manageable package).
This won't be fun...
Solder mask below the footprint is deliberately scratched off, I needed to probe that line earlier. It's also four-layer board, those seemingly unconnected vias are serving other layers.
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