The OP's post could have been written by me! I've been using a Windows PC since I started using a computer in '95. I've owned iPhones since they were released and had an iPad 3 for close to 6 weeks and will have the new iPad 4 soon. My current PC is past due for an upgrade (close to 6 years old). It will be nice to have everything tied in with each other.
I'm pretty good with iDevices but need to learn Macs a little. Liking bring my current documents over. I have about 150+ GB of pics saved on a portable hard drive. I haven't decided if i will bring them over to the Mini or if I'll just leave them there and keep added to that and my current PC. I like to keep them in two locations because I had one portable HD die. Luckily, I still had the pics in different locations. It's going to be like starting my computer life all over again (in a good way)!
Planning on the mid level i7. Maybe overkill for what I'll use it for (e-mail, web and some photo editing) but I rather have to much of anything than not enough. Like right now, I have 17 websites open, iTuens and Photoshop. Current computer works but it's showing its age.