I enjoy the OFF's up until the early 1960's issues. After that, until The Losers start, I couldn't care less. Same way with SSWS dino issues. For some reason I have developed a real fondness for All American Men of War. Maybe because it's a relatively cheaper run to collect than say OAAW or GIC.
Out of all the big five books, early OAAW issues seem the toughest to find. For every OAAW I see I seem to see five OFF's. OFF # 1 shows up on ebay all the time.
Yup, OFF #1 isn't that tough to find. Nor is OAAW #1 actually. The toughies for OAAW seem to be from #2 to #20.
Early AAMOW's are great, and as you said, they can be relatively inexpensive.
Dino's don't really do it for me either, but if you want the complete series, you've gotta buy those ones as well. I recently bought a semi-run of them in VG to Fine at a reasonable price in comparison to guide. That's the thing with those books, IMHO they are overpriced right now, so I will only pick them up for half guide or less (unless it's the first dinosaur, then you've gotta pay for it).
Andy