Comparatively speaking, though, modern *ix distributions are getting pretty resource hoggy as well.
Back in '02 or so, I grabbed Fedora Core 2 (or was it three) to take a look at the hullabaloo about Fedora - having come from environments like Novell NetWare and 'DTs' running Qnix off of a floppy, I was curious to see how well Fedora stacked up against XP on my machine that I had just finished building specifically for XP (I opted for dual 20 GB 7200 rpm HDs, splitting OS from data / programs, and building a custom XP install disc that automagically created everything correctly on the separate drives) - an I was so not impressed. I saved a whole 15 seconds on boot time between my optimized XP boot and Fedora.
Until I learned about kernels, and such. I plopped in a pre-compiled Con Kalivas (remember him? A Nurse by day...) kernel, and things started moving much faster. I then learned my way through compiling a kernel manually - IOW, pre-building modules that I needed for my machine, rather than having some sort of HAL poll my machine for every piece of hardware known to man and making me wait for a boot - and got that ...sucker down from ~1.5 minutes to 33 seconds flat.
That's 33 seconds total from pushing hte power on button to being at a login screen - and that included 8 seconds of BIOS and warmup for my Adaptec 29160N SCSI card also.
Default booting in mass-distributed distros today do still edge Windows and MacOS, but not by much. You want raw speed, look at Gentoo - steep learning curve, but totally worth it i the end.
I can still to this day compile a kernel for my system - I know what hardware I have, why make the system poll for hardware that I know is not installed? Why compile apps using basic i386 optimizations when I have a Core2Quad supporting SSE4 and everything i686? Why run apps compiled for KDE compatibility when I don't us KDE? (If I go with an Ubuntu-based distro, it's always Xubuntu - and in Gentoo I also install XFCE)....
Up above, when I said don't dual boot with XP, I meant don't dual boot *nix with XP - Although I am nostalgic about XP as well, and in its purest form it definitely is light on resources, it's also so wide open to drive by infections that until you install about 4 different apps, you're not really close to being secure. Unless, of course, you run as LUA as opposed to admin - then you're a helluva lot safer.
I've managed to push my RAM up - b/c part of that is because I push my machine hard, and part is because I like multi-tasking...lol. I have 4 GB installed running W7 x64 Ultimate (Thank you, TechNet!) an I have had over 3.25 used - but that was b/c I was testing a website in 5 different browsers, 2 of which had numerous tabs open in addition to the website in question, along with the usual suspects of apps I always have running. The big difference? W7 didn't care - it kept right on chugging along.
I may start working on a Gentoo build again, sine I plan on retiring this beast in favor of my Core i7 965 EE CPU (as soon as I can find it a decent home), but I am also toying with playing with WHS Vail, or putting OpenNAS on it and making it NAS, or even putting just regular old Gentoo and making it a NAS that way....
That, of course, is contingent on the time I have - and it looks like I won't have any, so....anyone want to sell me a really good x58 based mobo and 6 GB of really good RAM on the cheap? Poor college student and all....lol