Hi Suzy,
although i haven't yet tried the software (looks interesting enough, i'll give it a spin) just a few thoughts ...
From the tutorial it looks like the app is accurate enough at least in star-hopping mode - provided the internal sensors (compass especially) are calibrated.
My impression - after using other apps like Heavens Above or Mobile Observatory - is that the Night Mode most often is still much too bright, this is going to ruin your eye's dark adaption.
At least here in Germany there are lots of nights where moisture is a real problem - most Phones, including your Galaxy, will not respond kindly to being drenched in water ... well, the local phone dealer WILL - because You'll need a new phone
,You'll want a waterproof enclosing.
Most phones are also really heavy on the batteries when the display is turned on - my Motorola Defy lasts 4 hours max, i doubt your Galaxy is much better in that respect - so during an extended session You're likely to run out of juice ... that won't happen if You use a detailed, old-fashioned printed star chart.
Regards,
Steffen