From what we can see this new model addresses the only remaining issue for Raspberry Pi; its performance when running a full desktop environment or other memory and/or cache intensive purposes.
Last year we analyzed all this in quite some detail and we managed to extract a significant performance boost from the original Raspberry Pi simply by changing how we did things in software; we reduced our reliance the BCM2835's limited L1 and L2 caches and we optimized how we used the X server.
Display is a diagnostic tool which runs on Raspberry Pi, Windows, Mac and x86 Linux systems. We use it to compare the performance between different systems as far as things important to BitScope (and other real time graphical applications) are concerned.
It provides a good indication of how well suited a particular system is for running real-time graphical applications like BitScope DSO.
We'll use this tool to compare this new Raspberry Pi and its Quad Core BCM2836 chip with the original and post our findings as soon as we can. We're sure the performance boost will be significant; as Eben said "there comes a point when there's no substitute for more memory and CPU performance" and we agree. However, the beauty of this new model is that you get to eat your cake and keep it too!
All the work the Raspberry Pi Foundation and the Raspbian team have put into optimizing the software for Raspberry Pi will not go to waste. Indeed we expect that it will mean the performance compared to other distributions on comparable platforms will be even better than the hardware specs alone might suggest.
For many applications the Model A+ remains well suited but in our view the original Model B+ is probably only needed for legacy reasons (i.e. code compiled for the original will need to be rebuilt for this new model as it's now ARMv7).
We won't review this new Raspberry Pi in great detail here, there are many others who have had hands on experience who can tell you more about it including this YouTube from the Raspberry Pi Guy.
Lady Ada over at Adafruit also has an interesting review and of course Eben's original post is well worth a read. In any case, we'll make all our software available on this new Raspberry Pi just as soon as we can to take advantage of everything it has to offer!