With the release of the Montecito manuals I wondered about the relative sizes of Itanium and Pentium.
Below is a quick hack comparison between a Montecito dual-core
processor and a Prescott (early Pentium 4) core (I used this because
both were made with a 90nm process). I've very roughly chopped off the
L2 cache of the Prescott, and tried to superimpose it over the Itanium
core. Remembering the extra yellow bits are L2 cache on the Itanium, and
they roughly have the same L1 cache (16K L1I on both, 16K L1D on I2, 12K
L1D on Prescott) the Itanium core logic comes out looking about 10-15%
smaller. 
I got the Prescott die sizes from chip-architect.com and the Montecito sizes from the picture from Wikipedia article. If you want to check my maths, one pixel across is 0.0573mm and one pixel down is 0.575mm.
As you can see, the Itanium has a lot of cache. I will be interested to see how the Montecito stands up against the new Sun and IBM offerings over the next few months.