I've got about 14 vivariums full of them... Cool is in the eye of the beholder; not much mess -- everything stays confined to the viv.
Check Dendroboard for setup advice, but in general, once everything is set up, there's not much to do other than culture food. Staple food is wingless fruitflies, fed dusted with calcium (most folks using Repashy Calcium Plus these days), with springtails and isopods, particularly if you plan to raise froglets.
Vivariums can be about as complicated as you want to make them; what's mandatory is planted substrate with a false bottom (to keep the plants from sitting in water), and leaf litter (dried leaves). Lighting just needs to be sufficient for the plants, no UV or basking consideration. The vivarium needs a mostly glassed-in (only enough screen for a bit of ventilation) top, and the whole thing needs to be misted regularly. For ease of maintenance, you can drill a drain for the false bottom (otherwise it needs to be siphoned when full) and add misters (typically Mist King).
An 18 x 18 or 18 x 24 exo-terra with glass covering most of the screen top will suffice for a pair/trio of most species (one type of frog per viv, some species tolerate multiples of one or both sexes, others don't).
Actually, the first step is probably deciding what variety of dart frogs you want to keep; that will inform your tank choice and setup somewhat -- larger darts such as terribilus and tincts will need a larger (and perhaps horizontal) viv, smaller darts like thumbnails and pums (which are mostly what I keep) can get by with less room, and probably appreciate more climbing space.
This is probably a good point to wander over to dendroboard and dart den to get more of an idea of specifics.
Sorry forgot about this thread.
Thanks poison. Yes they are beautiful frogs & a great first dart species to start with imo. Their boldness, size & the fact that they can take much larger prey items than many species of dart frog. Makes them ideal for the beginner. A couple of mine, will even hand feed