CaptMorgan...
As a LONG time user of the 17" solely...both for business and pleasure (I run a small business and the Macs are our foundation)...I can't tell you how fond I am/was of them. It's all I used and we still have a pair in the systems...however, I did jump into the 15" rMBP. Primarily for my wife, our bookkeeper and client liaison. I couldn't believe it. I went out a month later and bought one for myself and I'm completely sold. From the Powerbooks forward, I've only owned 17"'ers. (?) --- however, after picking up the 15" with the 768GB SSD...and I do understand your storage woes. I was on the cutting edge years back pulling my ODD and supplementing my internal storage....the Thunderbolt and USB3 connectivity has solved any issues I have. As drive sizes have dropped...small, 1.5-2TB drives are a bargain, don't require a power supply and only weigh a few ounces...this is it. I'm never going back....unless Apple DOES indeed to decide to release a High Rez 17"
I think when 4k monitors become a bit more mainstream...I can see Apple re-releasing the 17" with a true 4k 'retina' display for the workstation and creative crowd. The Mac Pro has never been a big money maker for them either...and this new iteration looks to be damned spendy. I can see Apple bringing it back someday, in the right circumstances.
That said. It doesn't matter to me. The new 15" rMBP is everything I had in our 17s and much MUCH more. I can't tell you how nice the text is. Every time I open it...I'm happy. It's fast as hell...extremely light, the display is phenomenal and the I/O options with SD/HDMI Thunderbolt x 2 and USB3 alone make the leap a good one for me. I couldn't for the life of me get my USB3 express card to work from OWC. Transfer rates through that card were slower than my USB2 ports....I do understand your love for the real estate. It was my main concern. But the 15", I routinely run @ 1920x1200....actually 3840x2400 and it's absolutely stunning. NO lag, no issues with storage (again, a WD 1.5 TB USB3 drive is a hundred bucks...and takes up no room), and the ability to see every pixel in my canvas editing 1080p while the UI 'around' the canvas is pixel doubled magic for stunning clarity.
Honestly...one of the easiest tests for me was the 'App Store'. Open it in your 17" (Which is right up there as one of the highest, non-retina PPI displays with the 11" Air)...and side by side with a 15" rMBP. The difference is night and day. While I'm at a complete loss why Apple doesn't allow zoom or 'text enlargement' in the App Store, it's irrelevant on the rMBP. Completely readable whatever---9 or 10 point text they use. It's a pretty awesome experience.
I'm not trying to sell you on them. As I mentioned, I still own a pair of 2011 17" MBPs....both with dual drives SSD/HDD on the ODD side...I much, MUCH prefer to work on the rMBP.
Obvioiusly...and as always YMMV
I still have an old 17" Powerbook I use because of the larger PCIMCA slot. It allows the proprietary P2 cards from Panasonic to be offloaded in the field by simply plugging them in! The newer ExpressCard slots, other than for us adding SATA was really worthless....especially compared now with Thunderbolt x 2 and USB3....as well as HDMI.
J