First char (IA) probably took a month+ levelled up doing a bit of everything fp, space a bit of heroics all normal quests everywhere. It did mean towards the end I was so overlevelled but it was fun enough. Also levelled cybertech as I was going putting in my own mods in to the orange gear I got as I went (I'm still wearing the agent black talon agent coat) as well upgrading my ship mods.
I did start a second char (BH) early on as I thought rested xp might help (it doesn't for lower levels) and tried something which you can't do now which was a lvl 1 on fleet checked out all the crafting vendors for the codex's and bing lvl 4. Left that one gaining rest xp in a cantina.
Created 3rd (SI) after 1st had got to 50 and levelled quickly skipping repeat quests which wasn't many in the first 10 levels due to different starting planet but by lvl 10 was quite a few. Got to 14 (sprint yay) and did quite a bit of leveling through pvp as it was a lot of fun and then going back occasional side quests but most class story quests which I paid attention to as it's one of the best parts about the game is the storylines (hence skipping most of the planet quests)
About lvl 30 ish of char 3 I created char 4 (SW) and then rotated between the 3 so that I always had double xp going whenever leveling. between these I still did some dailies/weeklies with #1 as well as maxing out all the crew skills and affections.
As it stood yesterday
#1 lvl 50 IA healer maxed cybertech full pilots license
#3 lvl 50 SI melee dps maxed artifice lvl 37 valor
#2 lvl 48 BH ranged dps maxed armstech
#4 lvl 46 SW tank maxed biochem
I think around 7 or 8 maxed companions of all the various types
#5 & #6 I am aiming to run in 1.2 as sith/chiss republicans also maxing out synthweaving and armourtech.
Done a bit of everything but as someone stated above it takes 4-5 days (played) to max a char and for me that includes maxing crew skills and at least one maxed out companion. With the unlocks will be interesting to see what I manage now - rocket boosts, shorter qt but having not done anything republic side since beta I will be dragging my heels a little doing all the planet quests but with heroic force choke every 15 minutes on a smuggler it's going to be a blast.
Also something to mention is that after making a mint with #1 the others get supplied with lots of good gear which makes leveling really easy for me I'm glad I took cybertech first orange gear and making at least blue mods every two levels makes it easy to run through levels.