I tried the demo years ago and I really liked it. At the same time I also tries hexagon and loved it as well. Both are excellent modeling apps, although I do think that silo may offer some more tools, but hexagon was more logic in the way it works. In the end I bought hexagon, simply because of the price at that time, $1.99. Hexagon packs a lot of power and having used for a couple of years now, I'm still amazed at what it all offers. By now I'm not even tempted getting silo, since I've come to see that hexagon is an excellent tool and the price difference is too mucht between the two..... free vs 119 is an easy choice. Another thing is that silo has seemed to come to a standstil, while hexagon is still improving, be it very slow. Version 2.5 of haxagon may well be offering more then silo and  it's free, but doesn't feel like free or cheap at all. It's well thought through, has a hug range of tools and is easy to use once you take some time for it. Just because it's free, it doesn't mean it will not surprise you, on the contrary, try it you're in for a pleasant surprise..... it's a very complete modelling app.

Artwork and 3DToons items, create the perfect place for you toon and other figures!

http://www.renderosity.com/mod/bcs/index.php?vendor=23722

Due to the childish TOS changes, I'm not allowed to link to my other products outside of Rendo anymore :(

Food for thought.....
https://www.youtube.com/watch?v=pYZw0dfLmLk