My first job out of college was with Parametric Technologies (PTC) the company that makes Pro/Engineer. At the time Pro/E was the number one CAD software and I felt it was very easy to use. I worked for PTC for 4 years in various roles and did a lot with their modeling package called Mechanica. After finishing up there I've worked in the software industry for the most part, including a stint as a robot programmer. Pro/E is very expensive, but it's also really powerful, I really missed it's capabilities.
As part of a consulting gig I got to use Alibre Design which has since become Geomagic Design. It had all the power and usability of Pro/E at less than a tenth of the cost. At the time (2007) I believe I was able to get a full license for $599. When I started this project I decided to see what was available for a hobbyist class package so I tried out Sketchup, 123 Design, and FreeCAD. It's really easy to do simple stuff in Sketchup and 123 Design, but doing assemblies and motion analysis just wasn't easy or intuitive. After using a parametric modeler like Alibre going back to solids based manipulation feels unintuitive. I like being able to quickly and easily define a model that can be changed on the fly. FreeCAD is a decent attempt at a parametric modeler, but it is very buggy. I figured with how much time I'd waste working around it's bugs I might be better off paying for something.
I tried out Pro/E Creo and I was very saddened to discover that in an attempt to make things easier for new users they had made it unintuitive for people familiar with Pro/E. I'm sure that it demos really well, but I don't want to be held back by the UI and I just couldn't get a hang of it. After a couple of hours banging my head against the wall I decided to try out Geomagic Design which turned out to be a real eye opener. I had models going in minutes and was doing reach studies with the SCARA style arm prototype that first day.
Damn, they don't list the price. After the 15 day trial was up I contacted sales and was quoted a number North of $1000. It was tempting, but not that tempting. I spoke with the salesperson for a bit and he recommended I take a look at Cubify which it turns out is Geomagic Design and I was able to get a license for $199. Still seems like a lot, but I have been so much more productive since I've been using it that I really feel like it's worth the money.
I recommend downloading the trial and giving it a try. It's amazing how productive you will be.