OK Guys, Here is what has transpired - if you even care... ;-)

I HAVE a compressor already, so that isn't an issue.

The Bostitch RN45B doesn't have a depth of drive adjustment (air
pressure adjust - ugghh) , and the RN46-1 is a POS - IMHO.

The older PC 175 had such bad press I didn't feel the need to try out
the 175A version.

I ended up with the Hitachi NV45AB2. Got a fair deal on it at $289.
A lot of contractors use it around these parts.

I'll let you know how it all works out after I've:
Stripped the roof.
Replaced the rotten FG plywood and primed the edges.
Installed the drip edges the original contractor omitted!
Re-flashed and installed the Chimney cricket the contractor omitted.
Re-felted with 11 rolls of 30#.
And nailed 21 squares of OC Oakridge Pro 30 AR shingles down.

It could be a while...

Thanks,
Greg