Solar PV installation on flat roof

I've seen a couple of posts historically about people doing solar PV installs on a flat roof, but I was curious for a current sanity check.  I'm looking at some Solyndra modules that are quite cost-effective right now (no jokes please, I understand the company is a mess, but the technology was not the primary issue - it was the cost of building it).  They are designed for flat roof installation on a frame which is not bolted down.

Two concerns I've heard about this type of residential install are roof loading (which you'd think would also be a question too for sloped roof install, and these are quite light at <3 pounds/sqft) and the issue of not being bolted down (wind?).

I'm attracted to this solution because I have more flat roof than sloped roof to work with, the system can be more easily hidden, and I would avoid a lot of additional installation cost to re-roof my sloped roof which doesn't otherwise need it right now.

Any concerns on this approach?

Thanks.