What about hitpoints? Do you still gain them after you dual class?

I'm just about to start playing IWD and I was wondering what people think about dual-classing. Are there any draw backs or is it the best way to go? Should I start my mage character off as a fighter and then around level 3 dual class to a mage?

I used to swear by dual'ing my characters. I would figure out what the halfway point on the exp cap was and then dual everyone to mage so that they'd all be bad asses that could take anything.
In this one though, I'm starting to see that a fighter/theif/cleric heavy party really has some advantages. Later on (I'm not there yet, but I've heard) there are a couple of crossbows of speed to be had and if you have a high profiency in missile weapons and have a haste spell on your mage, that dude is downright deadly. I've seen the same thing with this high speed bow I picked up. It has what looks like 2 attacks per round (or 3/2, or whatever) and it's a badass piece of equipment. Anyhoo, long story short, I dunno, but that's just what I've seen so far!

You gain no hit points while progressing in your new class until you pass the old class by one level, from then on, I believe it's just one hp per lvl. Does that sound right to everyone?

P.S. I've decided that I'm going to finish the game with the party intact, then start over and use the XP cap remover to replay the game, dualing everyone to something else (except my paladin, of course, thought I may use a character editor to fix THAT little red wagon!)
That way, they're all novices again, but they all have high hp and lots of cool toys all ready!

If you dual class, you gain hit points in your 2nd class after you pass the level you were in the 1st class. The amount of hit points you gain is whatever the hit die your new class uses... for instance, if you had a fighter who got to level 4, but are now a mage, you would start gaining hit points again at level 5 in your mage class, and would gain 1d4 (+CON bonus) hit points per level.

Honestly, dual classing is too powerful and easy to exploit. This is why every powergamer goes right for it.