I own both 4430s and 4540s. I could tell that 4540s never gest even worm. Hardware monitor helps to understand the difference. My 4540s is also has Ivy Bridge, so it idles around 32° celsius. My 4430s has Sandy Bridge and it was idling around 48° celsius. To me, it was a bit excessive, plus I did not really felt any heat coming out of exhaust, so I decided to inspect the heat sink and sure enough it had al-cheapo thermal compound. I replaced it with Arctic Silver. Now 4430s idles ~ 42° celsius. So there is an improvement and yes, every degree counts! There is another thing to pay attention - Fan strategy. When we try to quiet it down - it may fall behind and CPU temp will keep going up, so is the fan speed. I think it requires some tweaking to get it well balanced. Of course, Ivi Bridge solves this issue by simply better efficiency.
BTW, replacing thermal compound is very trivial and simple procedure on 4430s laptops, not so on laptops with plastic cover like in 4530s.