Talking to other moms about their experiences switching their children out of the crib, whether you do it now or later, there's a good chance your son will "up and roaming around" when you switch him to a toddler bed or mattress. IMHO, why go and buy something else just to keep him in his crib for a few more months, when eventually you'll want him to sleep in a bed? For my own sanity, since he doesn't climb out, I would have rather kept my son in his crib for as long as possible. And if he had started to climb, I would have switched him asap, but now I'll be needing the crib in a few months, so we've got the toddler bed now.
It's been a little over a week for me, and I started when my hubby was out of town (so I'd only have to deal with one other crying and cranky person in the house instead of two ;-) I started a few weeks ago telling my son that he wasn't a baby anymore and that little boys sleep in beds. When the bed arrived, my son was so excited and loves to sit and play in it. When it came to actually sleeping though, he'd end up on the floor half the time. When he woke up and walked up to my bed, I'd just quietly get up and walk him back and pat him back down. He's down to waking up only once at night, and (now that my hubby is back in town and even though we've never co-slept) he comes into bed with us (so hubby can sleep--geez, you'd think I have 2 kids!). When my son starts to look like he actually enjoys sleeping in his bed, I'm going to tell him that "mommy isn't going to visit him at night anymore" and that "he's a big boy and doesn't need to visit Mommy and Daddy at night anymore", put up the baby gate, and just let him figure it out on his own. This is the only thing that got him originally sleeping through the night, and it only took 3 nights originally.
My son's Montessori pre-school teacher as well as my pediatrician all said to just put up the baby gate right away and let him fall asleep on the floor a few times. I'd have done it from the start, but again hubby can't handle hearing our son scream at night. Fortunately, hubby has a business trip in a month.
You may think your son is too little, but some moms I know have done it at younger ages and some as old as four! Sometimes the younger ones did just fine, some climbed out. Sometimes the 4 year old still climbed out and walked around.
I'm not sure if this is what you want to hear, or if this is helpful to you. But I wish you the best of luck and good sleep again soon!