No new questions this time around. I think you got me where I need to
be...

When you say keep the tub level with the rest of the bathroom, what
does that mean?

Just means that when I tile the bathroom floor for the tile I'll go
ahead and raise the tub floor too (as opposed to having the tub be a
1/2" lower which really wouldn't have bothered me that much but that's
not the way I'm going with it). Put another way, the floor is already
level across the stretch of the room including the floor that's under
the tub (or rather were the tub was before I took it out).

The backerboard can be done either way - either under
the tub or butting up to it. Doesn't really make a difference other
than you don't have to worry about a precision cut for the backerboard
if it extends under the edge of the tub

Right. The tub itself rests on 4 evenly spaced square mounts so those
are the important points to cover. Even so, I'll just put the BB under
the entire tub. The board will extend out beyond the tub a half a foot
before meeting up with another BB.

I assume you mean waterproof as in what you'd do
with a shower floor or something like that, so no, there isn't a need
to water proof. I'll leave a slight gap between backer board and wall
1/8"-1/16". I hadn't considered the reason for the gap is for the
expansion of the wood wall studs. That was a good insight.

Oh, when the time comes shouldn't I also caulk where the tile meets the
tub?

Absolutely. Caulk all changes in wall planes, wall to floor
transitions, around all edges of the tub inside and out of the wet
area, etc.

I figured as much and was just being clear. That's one of the reasons
they call it TUB & TILE caulk.

I'll probably go with modified then. Although, if you google on
"modified" and "backer board" you might be surprised to find that
there's some debate on this. I don't have the knowledge or field
experience to sort it out.

There's debate on everything, but having a little leeway with flex
between the floor and the backerboard can't hurt. The converse is not
true. It also simplifies your job by not having to keep switching
materials. If you're only doing one bathroom it's not a big deal.

The John Bridge Forums are another good place to get tiling
information.

That's one of the places they were debating the issue. I must say I
wasn't really clear on the points of the arguement, but I'm satsified
to go with the modified thinset. Thanks for helping me get off the
fence.

I guess I'm ready to move forward from here. Thanks again. I really
appreciate people like you taking the time to help out newbies like me.

People like me? People like me?! Crap - here I thought I was unique.

We were all newbies at one point. Answering questions here is my way
of trying to pass on some of the help and instruction I've received
over the years.

Do a good job and have some fun with it.

That's what it's all about (not to mention saving a couple bucks and
getting some time away from from my beloved wife). Thanks again.