I'm actually a Science student majoring in Life Sciences and I'm
from JC. My friends from poly were telling me they used up their
S/U options in their first semester. But like what MaNyZeR had said, they have less
S/U-able modules and hence, can afford to do so. After doing some
calculation of MCs, I have around 12 S/U-able modules to take in
total (inclusive of the 2 GEMS, 2 Breadths and 1 SS modules). And
out of these 12, I can only choose to S/U three of them. Thus, I'm
not sure if I should really exercise my S/U options right
now.
Personally, I find that it's really difficult to even get an A-,
let alone an A or A+. The cohort is very competitive, I would say.
And because NUS goes by the bell curve system, I find myself at a
disadvantage when the cohort happens to be really good. For
example, for one of my core module CAs, my raw score was around
40/50 but I was awarded with a C grade as there were just too many
people scoring full marks, 49 and 48. Then again, I couldn't S/U
that module if I did too badly because it's one of my core modules
and thus, not S/U-able.
And like what many have said, we can pull up the CAP over
semesters. But it gets increasingly difficult to pull up as time
goes by because the modules will definitely get tougher and the
impact of the results in our later years on our CAP seems to
decrease over time as well since we are taking on more and more
MCs. So is it true to say that the starting CAP we have is
important? And thus, we should try to get a CAP as high as possible
in our starting semesters?
The deadline for S/U option is tomorrow and I'm still very much
caught in this delimma. 
I just graduated from Life Sciences.
Haha, anything about modules wise you can ask me.
LSM1102 gave me a shock because that was the first time in my
life I got a D for a CA which I prepared for exhaustively.
Really have to warn you, year 2 will be extremely challenging.
LSM 2101 2102 and 2103 are very hard core. :p
I can understand the sentiment of A- being very difficult to
obtain..
Seriously buck up and study like mad. Not meant as an
discouragement but as a challenge to you. It only starts to get
"easier" in year 3. And much more fun, IMO.
And year 4 is very interesting, challenging and fun. If you take
the modules what you really enjoy..
Again, encourage you to S/U now. I never understood the
rationale of holding back S/Us. Or CORs bidding points. Its not as
if you can cash out $1 for each point you have in your general
account. but a lot of my life sci friends have thousand over points
in their general account when they grad, and only bid the minimum
required to get elective modules.
What core are you taking next sem? What electives are you
considering.