I appreciated being in the beta weekends as it gave me time to explore my alt-a-holicism and determine the class/race combinations I enjoy playing. Mostly I'll spend my first day or two creating all my characters and advancing them a little, then I'll focus in on my main (human elementalist) for the most part. Knowing me, I'll play long stretches on my main, and constantly swapping to alts as I work on the various crafting skills on alts so I can keep well geared on everyone. As I feel I hit a barrier in some zone or questline, I'll probably hop over to an alt, play it for awhile, then back to the main.
Of course, this is with PvE as my main interest. I refrained from dabbling in WvWvW solo (bad, bad experiences in WAR), so I could be completely captured by the concept once we start doing guild runs into it! :-D