Love Aperture3
Trevor,
First of all, if you are using the trial, update it. BUT, it will not update until you delete the Aperture preferences file, as noted below. In fact, contrary to what Apple claimed, I was able to convert my entire AP2 library and run it under AP3 in parallel with AP2. (Trust me, I kept safety copies of EVERYTHING. Time Machine is also a very nice safety blanket, but keeping a full copy of the old AP2 library takes up some serious disk.)
AP3 zooms along on my 4GB Mac Mini. Converting a 150 GB library took a long time and it helps to make sure that your previews are set to just under screen size and only 5 or 6 quality. I also have it set so that they are updated to share only upon shut down. LR is a bit clever in that it does not sharpen images except in full res; a real speed boost.
I have even started to play with faces - insanely great for finding all of those pictures of old girl friends. (Sadly does not recognize animals.) Brushes DO gag at full res on a 100 MB TIFF. The problem appears to be in the regeneration of thumbnails. Something not right here. I know that a "save" button is anathema in a non-destructive workflow, but we need to suspend a lot of these background tasks until we are happy with what we have done. Worse, the previously insanely great retouch, that killer of pimples, film scratches, and DSLR sensor dust seems to be badly broken.
Some notes:
-- Contrary to popular opinion, AP3 appears to be a major rewrite of the data base, thus everything related to conversion and update from AP2 takes a lot of time. Watch the little activity monitor near the bottom of the screen. If it starts spinning click on it and see what is going on. May be time for coffee. (This stops after a day or so.) Mess up the conversion and you will have no end of problems.
-- There have been two software updates and both seem to be important.
-- Start Aperture pressing the Apple and Option keys and rebuild the data base.
Finally, this seems to help a lot of people. (From the Apple discussion site.):
"Are you running the latest aperture 3 updates and prokit updates? If not, run software update, if you are - go to the finder and move everything to the trash that is inside these folders:
Hard Drive/Library/Caches
Hard Drive/System/Library/Caches
Hard Drive/Users/(Your user)/Library/Caches
Also delete this file:
Hard Drive/Users/(Your user)/Preferences/com.apple.aperture.plist
Reboot... It will take a little bit."
N.B. That last one was actually: Hard Drive/Users/(Your user)/Library/Preferences/com.apple.aperture.plist on my machine.
Don't delete the folder, just the files and folders inside.
"... a little bit." Translates to about ten minutes during which you will be sure that your Mac has died. Be patient. Once you reopen Aperture:
-- It will go into a long siege of processing. Looks like it rebuilds every project. Let it run and don't bother it.
-- Go to "Preferences" and reset everything as you wish. This is essential, especially Preview size and performance.
No guarantees, but while a vocal minority have issues, most find AP3 to be faster than AP2.
As for tools, you do know that most of the tools are turned off by default. Click on the bar marked "Adjustments" and a whole pile more appear. N.B. Most find the "Sharpen" is not very useful, but "Edge Sharpen" is VERY good. (Finally, if you need more tools, then you may need Photoshop or at least Elements!

)
Raw Developers are a matter of taste; especially for Nikon users. And while there are great debates about this, I find AP3 very good; certainly better at highlights than LR3b. (Haven't used CNX for years - can't get past the UI.) In any case, Rob Boyer has some great Nikon presets at
http://photo.rwboyer.com/. (See especially:
http://photo.rwboyer.com/series/aperture-3-nikon-presets/) He tends to be very anti-Aperture on Nikon color but I find that his D200 Landscape profile gives me the Nikon Look in spades. More to the point, once you see what he's doing, you can write your own presets until you heart's content. Most of Nikon's secret sauce is a kick more contrast/saturation/noise reduction/sharpening, once you get that, AP (and LR) can do Nikon all day. I actually prefer starting with the flatter image, but your mileage may vary.
If memory serves, this image was done with the Rob Boyer D200 "Landscape" preset. (It was certainly done with AP3.) Note the deep blue/green; classic Nikon.
This one was simply done by hand. Again, very dark and lots of green, but these are simply the AP3 base colors.
And finally, some mud. This is an overland forum, after all. (Lots of yellow/green.)
Rob also publishes eBooks on Aperture library structure, a subject that engenders much angst.
Bob Rockefeller is another knowledgeable soul on Aperture. You can read his stuff at:
http://www.bobrockefeller.com/
Finally, you can read all of the gnashing of teeth at:
http://discussions.apple.com/forum.jspa?forumID=1092 You will also quickly figure out who knows what they are talking about and who is willing to be helpful.
Bottom line, for workflow, tools, etc,. I think Aperture 3 nukes Lightroom. That said, if I were a Lightroom user and happy, I wouldn't bother to switch, most of my quibbles spring from lack of familiarity with LR, not actual problems. And LR3 final will be better and then AP4 will be better, etc. That said:
-- I love Aperture's full screen mode, especially on a laptop. I don't like editing in clutter mode.
-- Lightroom still lacks soft proof. Can't understand why.
-- Really like Lightroom's split screen before and after to watch edits. Pressing “M” in AP is close, but not the same.
-- The AP print module prints at full 16 bit and produces nice results, but has some bugs in the handling of presets, etc.
Hope this helps.