Is the difference between an i5 and an i7 dual-core procesor MBP really notable?

First of all, Koman90, the first MBPs that used i7 CPUs had dual core i7s, which were literally i5s with more L3 cache. Not much of an improvement in terms of performance compared to a true quad-core i7.

Second, HT doesn't make a 6 core CPU into a 12 core CPU. It only makes the CPU process more information at once, but will only make a difference in highly threaded applications.

Third, you CANNOT compare a Pentium 4 to any of the current Core iX series. Even per core, these i7s(first gen or not), will beat any Pentium 4 down without breaking a sweat....even if the i7/i5/i3 is single core variation at 2.0 GHz and the P4 is at 3GHz.

Back at the question though, the current MBPs have quad core i7s, unless whatever Apple store you are going to doesn't have stock of the latest MBPs yet.

As far as hardware, yes, i'm not a mac guy though so depending on the way OS X "Handles" the processor may make a difference, but for the most part i7 is MUCH faster than i5, i5 is a dual core processor with hypertreading (HT) ("feels" like quad core) while i7 is quad core with HT ("feels" like an eight core). i7 extream or i7-900 series is six core with HT ("feels" like 12 cores!)

for more info on processor architecture see http://intel.ly/ihkIFU

I just now realized that you said it was a dual core i7?! I don't think there is such a thing, i wloud get the 2.7ghz i7 by the current specs thoug as even if they are the same model, Dual with HT, that still equates to .3ghz * 2 cores * 2 threads per core = 1.2Ghz Overall difference, if you wanted to caclate the eqivelent Pentium 4 speed difference. Rember that formula as it is crucial in comparing processors; Clock Seepd * Cores (HT? *2) = Pentium 4 Equivlent.

Running an i5 on a MBP is good enough for me to do iOS programming.

If you want better, i7 would be good.