I've been using a short board (6'2" or so), since i started and it's tough..... and yes paddling is a friggon workout. I got back to the ocean yesterday after about 2 months, and wow.... it took me a good deal of time and paddling to make it to the break.
I have just barely started standing up...maybe done it about 7-10 times so far. it's really amazing when you catch a wave. Ive been wanting to try out a longboard, cause it's apparenly a lot easier to catch a wave on. But right now, my Rusty board will have to do.

I do agree with viachiangmai. it's both exhilirating, and 'calming'.... hard to explain. I just love the fact that it's a force of nature that can cause such emotions.