I know that Bethesda's intention is to give the player free choice in skyrim. But, If I want to get the most out of this game, should I complete the main quest first before doing side quests/factions? Or do factions then main quests? Because in oblivion, it mattered (to me at least) when you complete certain quest lines.

Im doing the College of Winterhold quests at the moment!

I havent been to the Greybeards yet

I'd like to know this too, but for me it's a case of wondering will the random dragons stop after the main quest line, much like the oblivion gates did?
If so i'll prob hold off the main quest line untill i'm sure i've learned every single shout/word there is possible.

I've seen some of the live streams before release and people said they're playing after the main story line (and there were dragons). Although, I'm not sure on this. However there's one difference between dragons and oblivion gates: The gates had to lead to premade dungeons, which essentially limited them (unless you repeat them at some point). As for dragons there shouldn't be any reason to not make them repeatable (unless the storyline keeps them from doing that) - names could be generated randomly.

Not recieved the game as yet myself, hoping it will arrive from Amazon this morning, if not it will probably be Monday.

Anyhow, In all the games from Daggerfall through Morrowind and Oblivion, I have always stayed clear of the MQ, and instead, freeplayed.

Only doing side quests when I had a conversation say after entering a shop or a tavern. Seems more natural that way for me personaly.
Of course I tend to sort of rp my characters anyway, ie a thief who only steals silver or a Hunter only hunting animals etc etc, there is massive scope for varied characters throughout all the Elder games for that sort of play imo.

An example being that I have had many, many characters over the years doing their own thing, acting out their own role. But, on the build up to Skyrim this past week or so, I did eventualy do the MQ as a parting (possible) farewell to
Oblivion, a game that has given me great pleasure since it first hit the shelves (it's fualts aside, (Mods are your friend on PC)). My intention on recieving Skyrim in the next day/s will be to create a first character who will
leave his prisoner existance and go to ground in the nearest friendly town, and try to get some work in one of the craft trades and go from there. He will maybe do a few jobs for the locals, get a love interest, sette down etc.
Once he has done this he will venture further afield and I will let his adventures develop as and when they do rather than go looking for specific quests or questlines.

Later I may well do as always and create a thief and other characters for the sort of gameplay that I feel like at any given time in order for my main characters gameplay not to become stale. Say spend a day or two theiving a day or two on a hunter then back to main character. rinse repeat. The MQ I may well only do on a specific character build more on the lines of a dedicated warrior build, but that will not be my main focus tbh.

Do as you see fit for your prefered playstyle I say.

And good luck.

Enjoy

Bump

Haven't heard of anyone who have finished the mq yet, but Since you won't die or anything in the end, there is probably no problem in finishing it,
I am doing a little bit o both, doing some random sidequests while traveling between mq-places.