I used some hockey skates for street skating about 8 months (and for indoor hockey for 2 years) - overall I'd have to say that the Powerslide and Seba slalom boots I've owned provide a better outdoor experience. But that said, there is no bigreason why not, since they're nice, light, cheap and turn on a dime.
But in answer to your question, the only real considerations are
1) The stock indoor wheels they come with get destroyed outdoors so will need replacing (mine lasted 10 days) - so add ┬ú45 to the cost
2) The lack of ankle support made some slalom moves and slides harder to master - and some landings were a little more hairy.
3) They don't filter out bumps in the tarmac as well as proper street skate - you really feel the vibrations
4) They're slower than the standard 4x80mm street skate setup (but turn better)
5) The shell is built to withstand impacts with a smooth indoor floor. Rough tarmac will wear it away much faster - I managed to put a small hole in mine quite quickly. YMMV.
None of them are deal-breakers, but it is worth keeping in mind.