In the Ergo their legs are spread apart but in a sitting position. I have a big hiking backpack that is nice but cumbersome and really only useful for..hiking! I LOVE my ergo and have used it for both my sons and a couple of kids I baby sit. In airports, museums, at the beach, around downtown shopping, you name it! It is truly worth the investment!
Do you have a local API group or babywearing group? They might help you learn other carries and get comfortable with it. A mei-tai is a simpler idea on that theme with ties instead of buckles.
Have you looked at
http://www.thebabywearer.com/index.php?page=choosinglinks
for research and advice?

Thanks for the reply! I was trying to find some information at that website today. I found a local babywearing group and am waiting for a reply to see when they meet up. Maybe it would be better to see people use one in person. I just don't want to use it and have my little guy uncomfortable.

I just bought an Ergo and I LOVE it for long walks and hikes. I have used the Moby wrap but my son didn't like to be confined, I use a ring sling for quick errands but that isn't very comfortable for either party for long periods, and I use a Mei Tai but it isn't great for long periods either. My son is over 1 year old but just a little bit bigger than you son at 18 lbs. I used to think that having his legs stretched out was uncomfortable for him but it never seemed to hurt him. He would definitely let me know if he was getting uncomfortable. Poke around the forum at www.thebabywearer.com. You'll definitely find tons of information there. It is a great resource.

You can do a hip carry position, that way his legs aren't apart so far.

Was he letting you know that he was uncomfortable or do you just think he looks uncomfortable?

I just got the Ergo in March for my then 6 month old, and it took me some time to get adjusted to it. I love it now! I have found that the keys in making her comfortable in the front wear are: (1) making sure her bottom is all the way down in the sling, (2) making sure she's centered in the sling, and (3) lifting her legs up in the sling that moves her bottom down, kind of forcing a correct sitting position in the sling. I've also found that it's crucial to play with the fit with the Ergo from the tightness of the shoulder straps to the correct positioning of the back strap. Even after all this time, there are times I find it not adjusted right. My husband hates it--can't seem to get it adjusted right for him.

That all being said, when it is adjusted well, I LOVE THE ERGO! It's the most supportive carrier I've tried (Moby and Baby Bjorn). Anyway, I don't know if this is at all helpful, but I just thought I'd pass my two cents along!

Good luck!