Available memory reduced ?

Question

I am running 10.6 on a Mac Book Pro Early 2009 Model with 4GB ram. 256Mb are allocated and shared with the integrated graphics card. This leaves me with 3.75GB available for application. Without running any major applications, only Safari, Mail and IChat I usually have about 600MB available.
600MB Available
800MB Wired
1.7GB Active
900MB Inactive
This strikes me a much lower than 10.5 was using. I never really looked that close in 10.5 as I always had enough to even run memory intensive applications like Netbeans and Xcode. Does anybody have similar experiences since upgrading ?
I understand that 64bit will use more then 32bit, so if this is the way 10.6 behaves I better get some more RAM. However if this is just some initial hurdles for 10.6 I'd rather wait for 10.6 before throwing away my current memory.
If you have any comments from your own experience or suggestions please let me know

Answer 1

(my math was wrong in the memory post... 64 bit can handle 16 billion gb (not 16,000))
2 more things.
Another benefit of 64 bit is that it should perform mathematical calculations 2X as fast as 32 bit (again, not positive)
http://www.apple.com/macosx/technology/ So you know i'm not making it up lol
Also, open up Activity Monitor and look at Virtual Memory too the far right. Its memory that hasn't been used in a really long time, so it is kept on the HD, which is much much slower than Ram, but still faster than dumping the memory altogether and then loading it again when needed.
So, you asked whether you should upgrade your ram: Not unless your computer is actually slow. Just because numbers tell you it's low shouldn't essentially mean anything unless you notice it, and 4gig sticks of ram are ridiculously priced at the moment.
A smarter idea may be to get a bigger hard drive if you're low on free space, so more Virtual Memory can be used. You can also delete files that you don't need, or also offload them onto an external HD instead, which would also be usefull for backup (you did say you use Xcode, and theres nothing worse than losing days of code )
(and by the way, I'm fine over here running Xcode and netbeans on only 2gb of ram, though if it really is slow I may just be used to it by now) <--joke