Can I have SL6 installed on my Desktop?

Absolutely. This has been the default for a long time, and existing systems can be upgraded in place. Note that as of SL6, we only support 64bit systems, and we no longer support storing permanent data on the local disk (/usr1/scratch is gone, only /tmp is available).

Can I install additional packages on my Linux Desktop?

As of SL6, you can install packages from our repositories (only), by choosing System -> Administration -> Add/Remove Software from the menu. You can't actually remove packages, only add them. There's also a blacklist, but that's probably incomplete, so please use your judgement and don't install software that could cause problems in our environment. If there's some package that you think should be installed on all Desktops, please let us know and we'll consider it for the default setup.