... If you choose to avoid migrating this stuff, you'll have to check for each type of data you want to leave behind. Moving some stuff, like a bunch of Word files, is as easy as copying; moving PS is darn near impossible and requires reinstallation; moving iTunes libraries is pretty straightforward; moving iPhoto stuff depends on how you have iPhoto set up. Again, easier to let Apple do it and then delete than to search around here incessantly to figure it out yourself.
From my understanding PS (or anything Adobe) is a lost cause, even with doing the initial setup migration assistant. It's one of the few apps I had wanted to move over until I read elsewhere that I couldn't anyway.
Your suggestions do sound like it'd be the most sensible approach, and normally, that's what I'd go with. However, I feel like I'd end up giving myself more work if I do it this way, because I only want to move over a few selected things. I'd end up having to do some massive clean-up afterwards if I used the setup migration.
A large part of why this is a dilemma for me is because the old computer will still be in use *as is* (with SL installed and most of the current files and apps intact). However, I do not want a majority of those in the new iMac. These two computers will be used for different purposes (and by different people). The few apps that I do need on the iMac will likely be easier to re-install than to migrate, such as the Adobe stuff. So with all that in mind, I've been looking for an alternate way to move some crucial stuff over only.
If push comes to shove and I can only choose between migrating completely or not at all, I may actually pick the latter. But that is of course not ideal.

After narrowing things down, I'm currently most concerned about Mail, my passwords, Firefox stuff, my iTunes stuff (mainly the apps and stuff for my iPhone and iPad; not the music and books as I manage those separately anyway), and miscellaneous app data. All the other stuff are really just files I can copy over without worrying about stuff breaking.
Oh and thanks for the pondini link - that looks quite informative! I'm gonna have to peruse it and see if I can find another way to do this.
Yes, my iMac arrived the evening of Jan 8, I set it up the following day. My machine had Mavericks installed.
I have found there is a work around for migration using your Time Machine backup,if you want to only migrate certain data or apps from Time Machine. I am attaching aYoutube video which explains the work around.
http://www.youtube.com/watch?v=akwS-tVqUus
The work around gives you complete flexibility on what you migrate. If you do the default Time Machine migration, you are limited to what you can and can not migrate.
If you use the default Time Machine migration and allow everything to migrate, your new machine will look exactly like your old machine, migrating users, passwords and all apps and data. It will just install all of your old apps and data on the new machine.
Thanks again for that video link! I've actually done that before to restore specific files in the past, but I had been wondering if it works for apps too and it looks like it does (at least for the simpler apps).
If I may ask, did you use this method to migrate any apps over? If so, did it bring over any user data or does it just purely transfer it over like a new install? By user data, I mean, say you bring over a chat app - will it bring over the login names or chat history? I'm assuming not, but thought I'd check anyway.
It looks like in the end, I may have to use the restore method like the one you linked - though I'd probably have to do some research on where to locate the files I need and where to move it to (things like Mail data or keychain passwords). Did you do any of those by any chance?
Anyhow, thanks all and I apologize for the convoluted replies and thought process. If anyone have any other ideas or input, I'd love to hear it!