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Let is begin by observing what a ridiculous name this card has. There is a GeForce GTX 650, a GeForce GTX 650 Ti, and now a GeForce GTX 650 Ti Boost. The latter two have a lot more in common with a GeForce GTX 660 than a GeForce GTX 650--or, for that matter, a GeForce GTX 660 Ti. Perhaps next generation, Nvidia will decide that Ti should mean slower rather than faster, just to confuse you even more.
If you get sufficiently confused, you can always throw your hands up and say, fine, I'm not going to buy any of them. AMD's naming scheme is, if not great, then at least a lot less bad. Whatever one thinks of the Radeon HD 7790, at least that's a different number from a 7770 or 7850.
So what is the GeForce GTX 650 Ti Boost, anyway? It's based on a GK106 GPU chip, which sports five SMXes split into three GPCs, together with three memory channels. The GeForce GTX 650 Ti disables one of each of those, leaving four SMXes split into two GPCs together with two memory channels. The GeForce GTX 650 Ti Boost fits in between these, disabling an SMX and a GPC, while leaving all of the memory channels active. Thus, the GeForce GTX 650 Ti Boost has four SMXes, two GPCs, and three memory channels.
Confused yet? You don't have to know what an SMX, a GPC, or a memory channel is to know that more is better. The GeForce GTX 650 Ti Boost is also clocked higher than the GeForce GTX 650 Ti non-Boost, so it will get more performance out of its hardware than a GeForce GTX 650 Ti non-Boost, even though it has the same SMXes and GPCs available.
Next, we face the issue that three memory channels naturally means you want 768 MB, 1.5 GB, or 3 GB of video memory. But Nvidia marketing has decided that those numbers are bad, so they fit the GeForce GTX 650 Ti with either 1 GB or 2 GB of video memory. Alas, this once again means that mismatched memory channels means you'll lose memory bandwidth if you use over 3/4 of the available video memory. The marketing solution to that was to send out "2 GB" cards for reviews (since few games will use more than 1.5 GB anyway), but not 1 GB cards.
Now, losing memory bandwidth is perhaps less crippling to a GeForce GTX 650 Ti Boost than it is to a GeForce GTX 660 or GeForce GTX 660 Ti. All three of those cards have the same memory bandwidth, but the GeForce GTX 650 Ti Boost has less other hardware to feed with that memory bandwidth. But a 1.5 GB card would still be far preferable to the stupid configurations that Nvidia is offering, and I'd recommend thinking of the new GeForce GTX 650 Ti Boost cards as a 768 MB version and a 1.5 GB version.
That brings me to my first recommendation: don't buy the 768 MB (err, "1 GB") version. That's just not enough video memory anymore. When even low end cards typically offer at least 1 GB--and let you use the full 1 GB in properly matched memory channels--you could easily run into problems from running out of video memory due to only having 768 GB available for proper use. That's probably why Nvidia didn't send out the "1 GB" cards for review.
As for the 1.5 GB (err, "2 GB") version, it's better than a 1 GB Radeon HD 7790 and not as good as a 2 GB Radeon HD 7850. It will typically trail behind a 1 GB Radeon HD 7850 as well, unless the 1 GB of video memory is a problem. We'll see where prices settle down, but the card should cost somewhere between a 1 GB Radeon HD 7790 and a 2 GB Radeon HD 7850.
As a new bin of an old die, energy efficiency comes in about where you might expect: it's about the same as a GeForce GTX 660. The Radeon HD 7790 was able to offer some real improvements in energy efficiency, so Nvidia didn't keep pace there. But even if they had managed to take 10 W off of the power consumption, that's not a big deal in a desktop. In a laptop, on the other hand, it would matter.