The last entry to this thread is a couple months old, but I'll chime in anyway since this is germaine to the larger discussion and, likely, something that everyone at some point in time will need to address.
I have become increasingly aware over the past few years (especially with my career change) of the cumulative effects of dust/smoke damage to the lungs. Now that I'm in my 50s, I think I've played Russian Roulette long enough that, if I want to avoid COPD or other such hazards, I need to be more careful.
I have also become more active in my woodworking since settling into the new career/job as well as my kids growing and moving on to their own lives. I noticed that, after a particularly aggressive woodworking session, I would end up sneezing/coughing for a significant period of time after I closed down the shop and cleaned myself up. The dust was a problem. I was covered in it and had been breathing it in.
Well, the external "big" dust is one thing: Wear an apron, wear a mask (I got an RZ mask). But even still, there was still dust EVERYWHERE.
My original DC was a HF 110v unit, no mods. This was, in the parlance of advanced dust collection and filtration experts, "piss poor". After the collection power of this unit became effectively nil, I looked into the wisdom of "the google" and found "the modifications" which I will not discuss here in depth since everyone knows them already or they can read about them in the 4000+ references that are easily findable with a search. Fine (and not so fine) dust was, frankly everywhere. The unit by itself was mediocre at picking up "wood chips and shavings", but ... Well.. Not good at anything else.
I tried the dust deputy solution with a Wynn 13F230NANO filter. I did NOT do the impeller upgrade. [I felt like, frankly, I was throwing good money at a bad machine with what I had done already (for some folk, this HF machine is fine. I'm not one of those folks).] Performance was better, dust capture was somewhat improved, but still not acceptable by the standards I was trying to reach. Fine (and not-so-fine) dust from the machines was still a problem because the vacuum power of the HF unit for what I was trying to accomplish just wasn't there.
You may ask why didn't I do the impeller upgrade and squeeze a little more out of the already frankenstein-inspired modified HF unit? My theory is that for the money I invested in the machine and associated upgrades to get a mediocre solution, I could find something for about the same money that would actually perform. I also do not subscribe to the "sunk cost theorem". In another sense, why try to solve a problem (with multiple, incremental changes to a product not designed to do what I needed) that has already been solved?
Enter: the Grizzly G0440. $600 on Craigslist. 100 hours or so on the machine. Squeaky clean. I am using the Wynn 13F230NANO filter (230 s.f. of MERV 15 surface area) on it instead of the supplied filter (90 s.f. of MERV 9-10 filtration) which greatly reduces the fine dust return to the shop and greatly increases the machine's ability to "breathe". This unit will be in an enclosed room with extra filtration on venting.
The G0440 is a significant upgrade performance-wise from anything the HF unit can provide and pretty much eliminates the "poor vacuum" issues that I was having. The first test of the machine on my saw caused a bit of a stir -- it pulled dust from places I didn't know could have dust in them! I tried running the machine just to filter air and noticed after a few minutes that the particulates seemed to be down. I do not have a particulate counter, so cannot provide objective data. However, I wasn't sneezing and coughing anymore and the "smell" of dust in the air was gone.
This (the new DC) isn't a solution in and of itself. There are many components to managing the problem (e.g. face mask, adequate ventilation, adequate filtration of particulates), but the dust collector is potentially the first issue to be addressed in a shop when it comes to dust management and air quality. If you don't have adequate LARGE dust collection, then you definitely do not have adequate SMALL/FINE dust filtration.
I am NOT trying to crap on the HF unit. As I stated, for many folks, this unit is fine for their needs and will perform. It is inexpensive and easily managed. Larger units are more difficult to deal with in a small shop (power, space, ducting).
YMMV, some settling may occur during shipment, get your parents to help you with assembly, don't run with scissors, always eat your vegetables.
<insert witty saying here>