1) Ubuntu 14.04 uses Unity 3D, which is based on Compiz. The whole thing is rendered through hardware-accelerated OpenGL. This is fantastic if you have good drivers and a good video card, not so much if either is missing.
There is absolutely no need to switch distributions. Just install a lighter desktop environment, log out, and log back in to the new desktop. For ease of use the preferred one is usually Xfce.
2) Combination of the broken update-apt-xapian-index cron job, and broken process scheduling in the kernel. Long story short, you need to append 'noautogroup' to your boot options, otherwise process niceness will not work. So:
- elevate to root with sudo
- in /etc/default/grub, edit GRUB_CMDLINE_LINUX_DEFAULT to be "quiet splash noautogroup"
- run 'update-grub'
This is safer than using the kernel.autogroup sysctl variable, which may panic some computers.
Anyway, contrary to what a lot of people say, Ubuntu runs fine with 1 GB of RAM if you don't use the bloated default desktop.
Edit: actually I filed a Launchpad bug about the second issue last year: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1219548