I'm not a huge fan of them at all. My mum had one a while back but it's rarely used. In reality if we want to see photos permenantly they'll be up there on the wall printed out, if we want to see them once in a while we'll look on the laptop when we need to do so.
Having something up there with the pictures constantly changing doesn't look very nice in my view... distracting more than aesthetically pleasing.
Interesting point about how hackable they are though - same goes with the cheap £30 sat-navs. I've been wanting to put some lightweight unix / linux variant on one of them for a while, just haven't got round to it yet.