Is it all it's cracked up to be? it's a little outdated now, but it is even as half as good as let's say a core 2 duo?

Core 2 Duo etc don't use it, was last used on the P4 as far as I remember, tho Intel are bringing it back in a different form with Nehalem ... http://www.anandtech.com/cpuchipsets/intel/showdoc.aspx?i=3326

How does let's say a pentium 4 processor with a 3.4ghz HT compare with let's say a core 2 duo 1.8ghz processor?

Don't know, I'm sure there are benchmarks around if you search for them.

It's not just speed, C2D consumes far less power and generates far less heat than the P4.