I always thought that air flow optimized fans are what should be used for intake fans. However I just read a post on overclock.net that since all intake fans should have filters, I should use static pressure fans. Any truth behind that statement, or should I just use air flow fans?
If the fan has something restricting its airflow, (heat sink, a bunch of HDD's stacked in front of it etc) high static pressure fans will help keep air flow up.
HDD's don't need a lot of air flow though, so I just left my stock fans (Probably air-flow fans) in place for the 4 HDD's and single SSD I run in my 400R (They run ~30C at idle and don't go over 35C when writing large files)
My take here is that it really depends upon the case design. If your HDD cage is removed, there would be little to no restriction on airflow (I don't think standard fan filters are very restrictive). If your HDD cage is oriented sideways (for easy HDD install/removal) then I think you can benefit some by having a static pressure fan (the cage does act as a restriction to airflow when oriented like that). If oriented front to back the restrictions would mainly be the HDD's you install, after two or so, you might want to look into a static pressure fan there.
Just my $0.02
edit: when considering case front fans
I suspect this also depends a bit on if you are using positive or negative pressure in your case cooling. For positive pressure, you are more likely to want static pressure intakes and flow optimized exhausts. For negative pressure, you are more likely to want flow optimized intakes and static pressure exhausts.
However, I doubt that the case pressure difference is going to be high enough to override other sources of airflow resistance. I don't know if filters provide much flow resistance, but I suspect they probably offer more resistance than even a poorly oriented hdd cage. Radiators are the main source of resistance that you'd need to worry about.
Worth taking into account is there are also "directed flow" fans with very high static pressure. These are designed as intake fans that focus the flow onto the components behind them. These are probably the best intakes fans for cooling a densely populated HDD cage.
The different types of fan also have different noise levels, with flow optimised fans being the quietest and directed flow fans the noisiest.