impressive, although i dont think i'd ever really use it. its surprisingly advanced, which is good - but being an advanced user, theres NO reason to NOT just get photoshop.
For power users, the lack of different color modes (CMYK, Lab, 16 bit/channel) or any kind of color management, curves (or even levels!), the kind of rich interaction (shortcuts, modifier-clicks, etc.) that desktop apps allow, serious retouching tools, line drawing tools, precise text control, etc. etc. makes this almost completely useless. Just the lack of the curves tool is frankly enough to doom any image editor (aimed at power users) which doesn't replace it with something of similar power.
For non-power-users, this is still missing important features, but it also has the same complex photoshop-like interface that has been confusing newbies for years. The learning curve of Splashup is steeper than it is for products aimed at casual users; they are better served by those tools.
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Clearly a lot of work went into splashup, and the technology will surely be useful for something--if nothing else it can be sold to some big company for piles of cash. But in its current incarnation it's basically useless.
But an image editor is really not the place for such tools, which belong in an organizer tool like Lightroom, iPhoto, or Bridge.