Can Macbook Pro replace a desktop?

You will be able to do what you need to with a retina MBP 15.

For future-proofing I would recommend making sure you get a MBP 15 with the separate NVIDIA GeForce GT 750M graphics chip. That will also get you 16 GB of RAM, and as you'll be manipulating 36.3 MP images, RAM will be chewed up fairly quickly.

MBPs have long been pretty effective desktop replacements for most uses, though you will actually save some money if you can live with an iMac rather than a MBP and will also end up with a faster machine.

Ultimately it's up to you and your need for true portability.

Macs come with a lot more features right off the bat, plus you will save yourself innumerable headaches in administering OS X as opposed to Windows. The time you'll save in not regularly updating your anti-virus software is a big one.

I can't tell you which platform will suit your needs better, but the fact that I'm here denotes my bias. 😝

But try it for yourself - go to an Apple Store and play with the 15" rMBPs without the dedicated graphics chip, and see if the performance level is acceptable to you.

I know several people who run Photoshop CS6 on MacBook Airs and are perfectly happy with the performance level they see; my recommendation was based on which Mac was best for your desired application.

Mostly I just want something that will work really well and last me for years, that I can do everything I need to do on, and since I'm pretty transient be portable enough for me to take anywhere. Can I get away with just using a Macbook pro and not have a desktop?

Macs will typically last for quite some time. The machine I'm currently writing this on is 4 years old and still working as well as it did when it was new (although I did recently have to replace a failed hard drive - no computer can avoid that). As an additional data point, my wife owns a business that has a small school for severely autistic children. I gave them an old Mac PowerBook G4 several years ago. At this point, that machine is 10 years old, and it's so badly dented on all four corners that it won't close properly anymore... and it still works! I've got an even older PowerBook G3 in a cabinet somewhere... if I felt the need to pull it out and use a machine so old that it doesn't even have wifi, I still could, though realistically I just keep it around for sentimental reasons.

As for not having a desktop, I haven't had a desktop computer in more than a decade. A good laptop fills the need nicely. If you need a larger screen sometimes, you can always hook up an external monitor. If you need very high-end graphics processing power, laptops can't really match what's available in a desktop machine. A 15" MacBook Pro should meet your stated needs, though.

I'm a graphic designer with needs similar to yours. Although I recently acquired a new Mac Pro, for quite a few years I did all my work on 17" MacBook Pros. You'll get much better performance with 16Gb of memory, especially when working with large photos. I've created files as large as 1Gb in Illustrator and InDesign and was still able to work on them in a reasonable way. (To calculate memory requirements for files in Adobe applications, the rule of thumb is 5x the file size when the file is in memory.) That being said, you will definitely want a computer with a discrete video card; it speeds up operations significantly.

I would definitely consider also purchasing AppleCare before it is a year old, as notebooks are more prone to factory defects than desktops. Note, user use and abuse is generally not covered by AppleCare, except in circumstances we can't cover here as we can't question Apple's policies. Don't attempt to second guess the cooling of a notebook, unless it shuts down on its own, as this tip explains:

https://discussions.apple.com/docs/DOC-2123