Pro & Con: side firing subwoofers....

I have seen more than a few full range, floorstanding speakers where the subwoofer was mounted on the sides. I have also read that this design can cause problems in smaller rooms.

Anyone know about this?
If you have to place them to close to the wall in a small room they could be a large problem for you. They can make the large floorstanding speaker look smaller by side placement of the sub, not as fat and ugly.
I don't like the idea of drivers facing in two different directions.

Actually, quite the contrary! in a small room, a sidefiring woofer is going to be easier to place with more flexibility...something you desperately need in small room acoustic space. Small rooms are very difficult to achieve "flat frequency response" in with a speaker(or several), and a good Parametric EQ on your bass woofer will do MARVELOUS things!!! ESPECIALLY when you're using floor standing towers with POWERED ACTIVE WOOFERS built in! You can EQ those speaker's bass woofers out for ruler flat bass response, which you can't do with just speaker placment in a small room! And, doing that, you won't affect your mid/tweeter any for sonic degradation any!...which is a huge plus! You'll still need good speaker placment as a foundation, but the EQing of the bass woofer will finish the job properly.
Also, if you have an 8' ceiling, the usual 2' from the floor woofer mounting location, on the side of most powered sidefiring floor standers, will even out the difficult 140hz bass mode you get from an 8' ceiling. The result of a properly place floor standing tower speaker with side firing powered woofers, "EQ"d with a good parametric EQ, using an 8' ceiling is likely going to work extremely well if done properly! You should be able to theoretically achieve very flat ultra dynamic, fast, accurate bass response from a scenario like that!..
So, I actually think you've got more potential with a sidefiring woofer speaker in a small room,if you just know what to do!
Good luck