I finally bit the bullet and did it. I replaced all my hot water lines with
PEX. This is one of those jobs I'd been pussyfooting around with. But
today for some reason I finally got the gumption up to do the entire job the
proper way.

What a colossal pain in the ass that was. It wasn't the PEX that was a
pain, it was getting rid of the galvanized that was the pain. Crouched down
in the crawlspace with the spiders whacking away at the foundation for 2
hours to open up the concrete just enough to get rid of a single 1/2" elbow
that was buried in a 6" beam on top of the foundation. I don't fear spiders
any more after that ordeal. The rest of the hour was spent pulling 3/4" PEX
line through that hole in the foundation and hoping the PEX wouldn't snag on
a nail or sharp rock. I ripped the hell out of the sheetrock in the garage
stringing the PEX up to the water heater - no biggie I'm replacing it all
anyway. I turned on the juice and voila - I forgot to crimp the 3/4" inlet
into my manifold. The amount of water was dramatic - especially since my
water is about 30 psi, maybe more. So after crimping that I tried again and
this time no problems so far. I have 2 lines that I suspect need to be
corrected, but I'll have to get to them later - the crimp ring is a little
too far away from the fitting for my comfort.

The difference in water pressure is astonishing - I can actually take a
shower without cranking up the hot water tap all the way. I might even be
able to turn down the water temp on the heater - right now its at 160 F to
compensate for the lack of pressure I was getting.

I tell you one thing, I had the 3/4" line suspended from J hangers in the
crawlspace to keep it relatively supported, after turning on the water the
PEX line sagged and expanded dramatically. It almost makes me wonder if I
should go back in and use something other than J hangers.

I ought to upload some photos of this, assuming it holds I'm pretty proud of
this job.