It created one for me: ram x 2and then there is using swap partition, Ubuntu's install doesn't create one by default.
yes, it works well on supported cards. you card's support (as well as mine) got dropped by ATI.... It ends up that "some people have good luck with the native driver and others need to get the right ATI/AMD driver for their system to work well". From what I read It seems to be differences in the model of video card, differences in memory on the card, and other system options, from chip sets, to other cards, to on board devices, to system ram, etc. that determines which driver will work best for you.
i never had the installer issues you are talking about. are you sure you have a good image download (md5sum checks out)?The 12.04 seems to use the same install program as 11.04, 11.10, I really think it needs to be fixed. The Ubuntu installers partition app defaults to setting up a 1 gig partition and no swap and leaves most of the drive unpartitioned. [etc]
i did have once ATI 9600 XT recognised as ATI mobility radeon. however one of the updates seems to have fixed that. if oyu hav/see an issue bug report it on launchpad. it cant'/wont' get solved unless someone that is "crushing bugs" doesn't know about it.