I'm at approximately latitude 35S, and it didn't seem to be much extra effort on my part to build an adjustable rack than a fixed one. I'm using four 140W Shell panels, so I put them in pairs on racks:
http://www.otherpower.com/images/scimages/236/solar_racks.jpg
The "stay" on the left is made up of two sections of square hollow section tubing, and each rack has 3 sturdy door hinges at the lower right. The racks are constructed from 25mm (1") SHS. They each cost about $100 (Australian) in materials[1]. I was happy to pay that, since each rack is holding $2400 worth of panels!
In the picture they're in the "winter" position, you can just see the bolt hole for "summer" on the rightmost rack, near the top. I've only drilled holes in the stay for "summer" and "winter", as that way I only need to climb onto the roof at the equinoxes. If I was enthusiastic I'd also have an "autumn/spring" setting, but that seems like a lot of effort for a minimal gain.
I found that the output at noon was prety much the same whichever setting I used, but putting them more upright meant that I gained an extra hour of output in the morning and evening, which helps in the winter. Those panels are rated at 4.7A max (@ 24VDC)), but I've seen as much as 21.5A from the array on a cold windy day when the sun breaks through the clouds.
BTH
[1] 12m of 25mm SHS, 1m of 30mm SHS, 3 hinges, stainless steel nuts & bolts to hold the panels on, galvanised nuts & bolts for the stay, welding rods, some scraps of 6mm x 25mm flat bar.
