My experience had been great!!!... Since the first time I went to surf I've been going 8 weekends in a row... At first I was obsessed with the idea of riding a shortboard, but well as you can see a lot of guys answered this post with wise things. Let me tell you a bit of my experience:
First class they gave me a 10'0 longboard, i got to stand in the white water in my first try
Second class was good and bad :S they gave me an 8'7 fun shape. It was kindda heavy but pretty easy to ride and stable. First try, the nose went down the water, the wave covered me and when i was going up I hit my head really hard with the board :S For a second I thought surf was a bad idea for me, i was scared. This class was really deep in the water so I could no stand. Paddling was sooooo hard and tiring. If you want some advise, go to work out in the gym, specially your back and shoulders if you want to progress your paddling speed and strength.
Next days I kept thinking about it and decided to keep on practicing every saturday + 2 days to the gym. Two weeks later I decided to test something a smaller, so I went for a 7'2 semi fun shape NSP surfboard. After several tries I got used to the board size and kept con practicing. For two weeks i kept on practicing on that 7'2 NSP.
Then I was decided to find a 7'2 to buy for me. I went to the store and when I was waiting for my 7'2 I saw a 6'6 NSP shortboard (ideal board to get into shortboards) so I asked for the test drive before buying the funboard, so i went to try the shorty. Paddling was muuuuch harder and staying on top of the board was difficult. First tries I fell in the water, but the... i stand up and ride a wave... gotta say it was amazing!!! so I decided to buy the shorty because I was afraid to spend $450 in a board i will get bored in about 2 months. I got myself a brand new 6'6 NSP Epoxy Shortboard
I used her last saturday and catched lots of waves
So 2 months later here I am... in my shorty wich at first i thought it will take about 6 months or even more.
Really, work out a bit if you want to be able to be in the line-up without feeling you need an ambulance or you can't paddle anymore. Going to the gym and being constant (every saturday - 2 sessions if possible) was the key to my success. I'm not a good surfer yet but at least I have confidence, I'm fit and I love surfing. Gotta say I struggle to get in the line-up because duck-diving is kindda hard to learn but well, is all about practice.