Vanguard is really fun and mobile in pvp, and you can take quite a few hits (note your still screwed if you try to bite off more than you can chew) PvE they might start off a little slow killing/soloing wise, but later its all smooth sailing. With healing pet can solo most heroic 2's up till around 40ish (companion skills just don't scale that well) Just note, don't play this class if you don't wanna hit things with the end of your gun over and over, you'll use stockstrike like 1000000x =P.

Note that its been mentioned they are looking at adding a "neutral" set of gear for those that stay in the grey area, my guess is it'll require certain amounts of both light and darkside points or something, so while yes light and dark side have a few cool things they can use now, it might not make a difference in the future.

Try to keep out of sight as much as possible until enemies are engaged with other friendlies, then start laying down some fire, if anyone peels off on you, stun/root, and try to keep distance. Also dirty-fighting has some great things for pvp for gunslingers. Gunslingers aren't gonna go rambo mow down 5 people in a row, but if you can keep ranged and pick good targets, you can be extremely effective.