Wow, sorry I missed this post.  I also want to welcome you to the world of Macs.  Been using them forever (well since about 1984 when they came out...) and will never use anything else (I have a PC here, but that's more for playing obscure games because I don't wanna install Windows on my Mac).  The learning curve is easily overcome as I know plenty of others who have switched and have had an easy time with no real regrets.
I agree with Rui- iPhoto is great for importing and managing your photos (I use it for that purpose and it had no problem recognizing my Nikon P5000), but Photoshop is the industry standard and very well supported for your actual manipulations.  Office is good for all nearly all your other needs.
And if you want to get into 3D, the program I use (History With Dade, AFO, Admiralty instructions) is Cinema 4D.  A fast program that has crashed on me less than five times in almost ten years of use.
The iMac is actually very powerful- I had always used tower Macs before, but the Core2 Duo iMacs do nearly everything I need for a fraction of the price and with excellent monitor built in, so when I upgraded from my G5, I bought an iMac.  Believe me when I say that if this thing can handle the kind 3D stuff I throw at it, it can handle almost anything.  My girl just got an iBook that is also the bee's knees, so if you ever want a lap top, I recommend the iBook.  Enjoy and have fun!  
