I had some responsiveness problems in Tiger but I thought they were my HD. 10.4.3 seems to improved things a lot though.
OS X eats RAM I'd say 512MB is the minimum.
As for being bloated... it's not quite as bad as it sounds , Half of the Tiger install disc is printer drivers. There's also all sorts of OSS software included web server, FTP, there's also development tools such as Python, Perl etc.
It's big because there's a lot there.
