I just bought a 21.5" iMac - the 2.7GHz model. I did it for a few reasons; though it was immediately prompted by the Lion requirement for iBooks Author.
But my three year-old MacBook Pro was starting to feel a little confined; it really needed more memory, and the SuperDrive had stopped working, which amongst other things, was going to make it difficult to upgrade with the Lion install disk I had!
And secretly I'd been wanting to get a slightly larger screened, faster machine with more memory. It just seemed right to get an iMac, though I'll still be using the MacBook Pro.
Here's some notes from the experience so far:
Why not the 27-inch model?
I bought the smaller model iMac not so much because it was cheaper, but because I just came to the conclusion that the 27 inch iMac was too huge for my liking. I mean, it's HUGE!! The 21.5 inch screen is plenty large enough for me; at least at the moment, though this is coming from someone who has mostly been using a MacBook Pro and smaller external displays. The 21.5 inch screen seems large enough for me.
I'm ordering a 16GB upgrade for the machine. I'll probably get it from OWC; they have a great reputation for memory and I've bought from them before. One nice thing about the current iMac design; replacing the memory seems to be pretty straight forward.
Bluetooth keyboard and mouse
This is the first time I've had a wireless mouse and keyboard. It will be interesting to see how this pans out. So far, I'm having a little trouble getting used to the way the scrolling in the mouse works; which is opposite what you're used to if you have a mouse with a scroll wheel in it. I know you can change the setting in Preferences, but I'm leaving it as is for now.
Wi-Fi network issues
I've encountered an odd problem with the machine not detecting the Wi-Fi network when first started. Restarting solves the problem. A thread at Apple's support forum suggests that not turning on the keyboard and mouse during start-up will solve the problem. I will have to try that.
Barely gotten to know Lion so far, so I can't really comment on it yet.
Adobe Serial Numbers
Another reason I decided I needed to get an iMac with more memory, faster processor and bigger screen is I'm hoping to spend more time with After Effects. So one of the first things I installed was Adobe Creative Suite.
As always seems to happen, though I could find the discs, I couldn't find the serial number; did you know that if you have registered your software with Adobe, you can go into your account and find out your serial number? That's useful; and saved me searching all over the place!
And Adobe does allow you to install the software on two computers; as long as you don't run it at the same time on both!
It is nice to have a new machine to play with!