The main problem with them is finding a tidy place to put the fan, and keeping them cool.
S_Natural gave some good tips, also adding another fan to make it push+pull radiator helps.
What I would suggest though is to install water cooling. Temps are easily down 10-30 celsius depending on your setup, gpu is fanless so it is silent and as a special bonus it becomes a one slot card, block+card+backplate is only 21mm thick.
They pull almost nothing from pcie slot so no need for risers. Add long tubing + radiators outside and you have a dirty powerful rig without heat/ noise problems.
Also avoid automated driver updates at all cost, as some of the more modern drivers will break your cards.
Easiest workaround for this is to roll back drivers in device manager, windows will ask reason for this and stops autoupdating.
Cards use bfr memory, modding straps gives a nice boost to equihash, from 660 closer to 800. Cryptonight gets some boost too, last time I tried dagger was unaffected. But that was many many dags ago so things could have changed.
To sum it up, if power is no problem and you have enough psu's and quality power cables+connectors, 295x2 is still a really nice toy to play with.
edit: It isn't a 8GB card, it is a 2 x 4GB card. So two turkeys doesn't make an eagle there...