paulw1283:: ... must we attain the same kind of proficiency as in regular nose out hover ...
... practicing sideway hover ... I broke the blade (no other damage, thankfully) ... I also got nervous ...
Profiency level is different for each pilot. At what point do you say "I'm good enough"? If loosing control and crashing in that orientation is "good enough" for you then ... yes ... why practice at it any more. However, if you feel the desire to be able to not crash in that orientation then I'd say you need to practice more ... become a little more proficient
paulw1283:: ... But is it necessary to be able to HOVER it at a stand still?
Necessary is a strong word. There are only two things necessary in the RC heli hobby ... enjoy yourself and don't get yourself or anybody else hurt.
The RC hobby is about being able to do something that most people can't do (yet). Being able to confidently control your heli in any orientation is a big confidency booster. Remember when you were able to hover a whole tank in the tail in orientation. Remember the sense of accomplishment. Every (successful) accomplishment of a new orientation or new maneuver should bring the same elation.
Just remember, the orientation that you decide that you don't have to be profient at is the orientation the heli will invariably end up in. You need to be at least a little proficient at that orientation or be very good at getting it to a more comfortable orientation before it crashes.
Good Luck,
d.tipton