Major Update: http://www.drrevan.com/2011/12/patch-101-notes.html
They nerfed slicing
So most non-rich yield missions are turning negative returns and rich missions on average are returning 40% less credits per minute than before.
So if you want to continue to do slicing, only do it with rich missions, but don't expect as much of a return.
Excerpt from my blog
http://www.drrevan.com/2011/12/why-y...t-slicing.html
Why you should get slicing.
The profession system in Star Wars: The Old Republic is absolutely excellent. There are a small number of gathering professions, a large number of crafting, and a few "mission" skills which your companions can help you gather rarer items.
You can find some great guides to professions at http://www.starwarsmmolevelingguide.com/crafting-guide/
I'm not going to cover all of the professions, but I do want to talk about the slicing profession and why you should get it immediately instead of a mission skill.
When you pick up slicing, it grants you access to nodes found in the world which contain credit boxes. Right click on the credit box and you will get credits. Simple enough. You also will have the ability to send your companions to level up this profession as well. Simply choose the missions which give you lockboxes and you can and will earn credits. The initial missions cost 95 credits to send your companion, but I have received boxes with up to 300 credits in them. In my last mission yesterday, I sent my companion on a mission which cost 300 credits to get a lockbox with 1200 credits in it. Simply put, every few minutes you send your companions (you can send up to two at a time) to gather free credits for you. Do this as often as possible.
Now, at the highest level, it might be that slicing is a bad profession, but slicing will always provide you a steady income and for leveling that income will help you buy your speeder, gear, mods, and upgrades and low level rare items wont' sell as much since people outlevel everything pretty quickly. Once you reach level 50, you can consider dropping slicing to pick up a different mission skill related to your crafting skill since you will need the rare materials, but until then, free credits slicing is definitely the best way to go.
More evidence: I got slicing two days ago after I reached level 20 in game. I started with 10,000 credits. After playing for 6 hours and constantly sending two companions to do slicing, I now have 26,000 credits. Only about 3000 of that is from quests since most of the time I wasn't actually doing quests.
This is why you should go slicing while leveling and don't look back.
tldr; Slicing gives you credits. Credits are good. Get Slicing.