People armed only with a simple understanding of EFI operation has plagued the backyard mechanics' opinion of an FMU. The theory is that the ECU monitors manifold pressure and when it sees an increase due to boost, let's say 6 psi, that it increases fuel pressure by 6 psi and everything is good. While this is true, it doesn't take into effect the differing needs of air/fuel ratios nor the increase in temperature due to boost which are the purposes of an FMU.
While this is fine under N/A applications (where you are likely to see the 4 - 6 psi difference in delta P) it can be dangerous in a boosted application. Most people are able to get away with not using an FMU because they stay in the mild to moderate ranges of boost (4 to 8 psi). The problem arises in the lack of injector pulse manipulation. Because airflow determines fuel flow, modifications for increased fuel flow must be made. Most people get around this by simply stepping up in injector size and thereby kill idle characteristics.
The only viable option I would be willing to recommend to someone is a rising-rate regulator. Rather than simply raising fuel pressure on a 1:1 basis, you can set up a higher ratio which forces more fuel through the injector without increasing pulse duration.
Any way you decide to go, I highly recommend you either talk to the tech guys at ATI or someone at a local speed shop who is knowledgable in tuning and installing superchargers.
It's your money, you need to decide what you can afford not to do and what you can't afford not to do.