Reply to mikeselectricstuff and elmood:
#1/#2: Open loop steppers: OUCH. That makes backlash in the x,y drive mechanics a potential problem, as well as bends and warps in the general mechanics. If they're smart they can attempt to compensate for backlash with clever software. For example, if they know where the nozzle is over the camera, and they know where the final placement location will be, they can step the motors several steps (maximum backlash distance) towards the final placement position before they stop to take a photo of the part. MAYBE (depends on how this might interact with PCB reference marks).
You get what you pay for. You mustn't forget these machines are maybe a tenth or less the cost of anything you could buy a very few years ago.
They are creating a new market that simply didn't exist before - low cost, low(er) performance
You want sub-micron servos and granite bases, talk to Mydata, Juki, Essemtech etc. and bend over.
#3: Tall parts: Probably any part over a few millimeters high can be placed well enough by hand.
Unless you have a large number of them on the board. IMO this is one of the less necessary shortcomings of the Chinese machines.
#5: Competition: The smallSMT machine with servos appears to cost about $12K with some feeders, which is roughly the same as the neoden4. They do have some smaller stepper-motor machines, but I doubt I'd trust them. Also, they claim they support only as small as 0402 and I need to support 0201 or smaller (required for some of my BGA components that I need, which means I'm sure to run into this same requirement in the future). I'm not sure why the servo-based machines are not accurate enough, unless it is what seems like the classic silly mistake that cheap pick and place machine designers make (200 step stepper to rotate parts on nozzle).
Small parts are not just about placement accuracy - things like feeder performance become increasingly important - parts not bouncing out. Also nozzle design and vision becomes harder.
Stuff like 0201s are still regarded as a bit exotoc by many assembly houses - Chinese are aiming at a higher volume market than the big guys, I'm not sure we'll ever see parts that small being supported on cheaper machines.
Requirements: I absolutely need to place 0201 discrete components and 0.50mm BGAs and QFNs (and maybe 0.30mm later on). On the other hand, I do not need speed, as I'm only need to build small batches of prototypes and demos units (at the moment, anyway).
In which case I suggest you increase your budget or spend time looking for a good subcontractor with a high end machine.
Not needing speed isn't really going to save much money as most of the market for tiny parts is for high volume users, so there isn't enough market for a machine with high accuracy but low speed for anyone to put in the R&D to make something that can do it with a high degree of reliability.
#7: Solder Paste: A couple people I've communicated with claim most of their defective PCBs are due to imperfect solder-paste application.
Absolutely - paste quality is the biggest factor in final board quality.