It looks like I'm in the minority, but I had MAJOR problems once I moved my not-so-great-sleeper 2 1/2 ds to a big bed. I think it just provides them with so much freedom and yet they're too young to fully understand limits and consequences. I'm a big fan of keeping them in their cribs longer, so that once they do move you can reason with them better if there's problems. A month or 2 after moving my ds to a big bed, he started getting up at bedtime in excess of 50 times a night!!!! It took a long time to break that new digression.
If you're having trouble with your ds climbing out, consider a crib tent (the only problem is that it can provide them with a distracion - my ds spent lots of time trying to unzip from the inside out!) and also a sleep sac, as then they can't really get their legs high enough!