Windows 7 home premium works on 512 ram too(professional edition and above it don't work below 1 gb ram) , but lags slightly. But that and processor is not a major prob, The biggest thing is Graphic memory, integrated GMA 900 , 950 doesn't do well with it, most of the graphic memory is taken by aero theme itself, leaving very little for other works, So it lags if some kind of Graphic drawing takes place suddenly. Specially if its a game, If u have any intel integrated graphic below gma 3100, don't install games on windows 7. They won't give proper fps = won't work.
any graphic card dedicated would do, even 128 MB cards, nvidia , ati both will work very efficiently.
other problem is harddisk access, both vista and win 7 show that, specially if u r running old Parallel ATA based harddrives. New SATA based doesn't much has problems. But Still All those people whos system lags a little, or hangs at time for few second, Consider Shutting off virtual memory, Thats is paging memory inside a hdd. That will improve working performance. And if u don't wanna switch it off, Just make it to minimum required which is 377 mb or more , So that windows can work virtual memory normally and Can write Errors reports and Other data If ever ur system crashes.
people are saying win 7 is pretty much same as vista, Yes at the core it is, not much of a difference. But at performance its much better that vista. copying, installation, compressing, encrypting etc all works faster in win 7. Even task handling and dumping.
win 7 eliminates all major weaknesses of vista. I have been xp user for years. I used vista only twice for 2 days each, i never liked it. But win 7 is performing really good, Even better than xp in some areas. Not graphic tough.
any os after xp is graphic resource hog.
But ill still say win7 is better.
in its rtm and rc stages it showing slight compatibility problems with old softwares, but its still working. lots of softwares don't work, Specially antiviruses meant for lower os. Drivers not working. Compilers, like old visual studio 2005 it also giving errors. some other softwares which include hardware accesses give errors sometimes too. Old 16 bit softs r not working at all.
But any new software made for vista, or win 7 r performing much better than vista. win 7 already included most of drivers so Not much installation is needed to run hardwares.
I would say its an improvement shown by microsoft with releasing win 7.