There's a possibility I'll be switching to a MacBook Pro as my development machine at work. A few years ago, before OS-X, a switch like this would have made me feel a little worried. I'm productive in Windows. One of the reasons why is how I arrange my Windows environment to mirror, in a sense, the Linux and Solaris machines I typically develop software for. OS-X eliminates that distinction. As for software, I use a stack of free and open source applications that have analogs on OS-X.
Eclipse (has a Mac distribution)
Sun's Java SE SDK (has a Mac distribution)
Python (has a Mac distribution)
ActivePerl (has a Mac distribution)
WinSCP and PuTTY (Fugu and Cyberduck)
Emacs (has a Mac distribution)
wikidPad (runs on a Mac)
Cygwin (OS-X has Terminal :))
IfranView (iPhoto)
Inkscape (has a Mac distribution)
Subversion (has a Mac distribution)
Trac (server side, browser accessed application)
I use iTerm instead of Terminal when SSH is needed. I tried CyberDuck but Fugu is more suited to how I work and I deleted CD.
As for Notepad++, this is one instance where I splashed out cash and got TextMate, which has been worth it for me.
Come on over, the water's fine!
p.s. Hope your back is feeling better.
I knew it was only a matter of time before you would give in to the Shiny Shiny. ;-)
I recently upgraded my well-worn PowerBook G4 with a fully tricked-out MacBook Pro 17". Do get the largest screen you can afford, as you're probably well aware of the advantages of wide-open spaces in software development.
As to software, I'll echo BST's recommendation of iTerm. And Python, Perl, Emacs and the JDK *come* with OS X (the latter in the separately-installed Developer Tools) -- no need to download a separate version unless the stock install doesn't fulfill your specific needs.
You're going to want TextMate rather than TextWrangler ...