open aperture.
click on "aperture" in menu bar.
in the pull down menu click on preferences.
in the pop up box, under output, it has a space called external editor. click the choose button, and in the window that pops up you can navigate to photoshop and click choose.

I've done duo tone twice, both times with sets of images for printing large volume runs of calandars, both times in photoshop.

you can create a new version, and do the side by side comparison easily.
you can duplicate a master image if you choose.
whenever you edit an image, your original is untouched.

goto your adjustment hud, click the little symble in the corner to get more tool options....from there you'll find the monochrome mixer. That is the black and white panel that really works amazingly well.
tint and toning can be done using the color controls.
I haven't tried duotoning, in aperture and not sure if it does that...

The first thing you need to understand is this...Aperture and lightroom are workflow tools NOT photoshop replacements...

for those who only use photoshop to do color, density, cropping, raw processing, noise reduction, and sharpening, you will find aperture does all that. Apeerture allows you to make your adjustments on one image (including raw, straight out of the camera without any other processing) and then click the lift tool, select all the other images (hundreds at once if you choose) and stamp those adjustmens to as many images as you selected (ie you shot dozens of images under similar lighting conditions, and all of them need the same color balance). It will complete the task in half the time it would take photoshop to launch, never mind opening a file.

for those who need layers, masks, and other advanced photoshop features, you select you images in aperture, righ (or control) click the selected images and select "open in external image editor" (which you set up as photoshop in you preferences) do your photoshop majik, and close the image in photoshop and it turns up in your aperture library, as a version of your original. your original is still there, unaltered. that's round tripping.

set you metadata and keywords on import or after import.
it helps to think of a stack as being a stack of prints or slides...when you're sorting them.

set the auto stack feature and your images will be sorted for you...for example set the auto stack to 3 seconds and all images shot within 3 seconds of each othe wind up in a stack (burst mode shooting, but intervals can be set for longer as well) you then go through the stack, choose the best one by checking it, and close the stack. now the only visible image from the stack using space on your screen, is the best one.

the lighttable is familiar to many "Old school" pros that layed out thier slides on a light table for sorting, viewing an making selections...
The light table in aperture is meant to emulate that type of workflow, and to the best I've been able to discern, works especially well with multi monitor set ups. I've used it a couple times, with my projector, having images and stacks on the projector display, and contols on my laptop.
on a 30 " cinema display is where it'd really show it's worth.
have you tried the auto stack and stack features? the lift and stamp?
do you know how to "round trip" an image from aperture to photoshop then back to aperture?

I believe that your affection for Ilife makes the descision for you....
Aperture.
feature for feature there's little to seperate the two...until you factor in Mac-centric items such as intergration with osx, ilife, applescript, automator....
here's a good read to get you started......
http://digitalmedia.oreilly.com/aperture/

at f2.8, and weather sealed, I'm assuming You don't want to venture out there...your equipment is certianly up to it!
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can't wait to here all about it and see some images...will have to wait till Christmas before I can get one...javascript:emoticon('')

All these years and only two bridezilla's...

One pretty much wanted everthing for free, and wasn't above slander and lies to get it....never worked without a written contract since.
and anoyher that propositioned me...on the morning of...one last fling...blah, blah, blah....I told her I was all for it, but she'd have ask my wife first...

now I'd have to write a whole book about all the good ones!!!
People at weddings are either at htier very best or thier very worst...but they're never normal!

you all know Gerri and I share.....sometimes it really boils down to learning to like the stuff she don't like.....

my kids grumble about my flavour of chips: "Dad, why do you buy those...they're gross?"
"Did you eat them all on me?"
"Ewwwww! No way!"
"I Don't know why I buy them...I just do"

Gerri don't like beer: "Don, why did you buy that? It's gross..." you get the idea....

So I grab the ds2, knowing nobody's messed up the settings, and left the batteries uncharged, and memory card half full.
So I grab the manual lenses knowing there's no dirty specs or prints on them...

Divorce Costs alot of lenses, and so what if I did buy her that 50mm macro I always wanted for her birthday, last month.....

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looks like it could be handy..while jumping out of an airplane....
but I'm not really a big fan of them....can't honestly say dropping cameras is a common enough occurance to justify the cost...however, setting one camera into a kitbag and grabbing another, while in a hurry, is a habit.....so straps, brackets, hotshoe covers etc are more of a time waster than an insurance policy....
To each thier own...

well....at least we're talkin lenses here, not computers....Pentax would be shiping brand new 486's....next month....