For a 1st time bike purchase, here's what I recommend:
1. Ride every damn bike in the store that they have in your size. Ride the same test route. Shift through all the gears, etc.
2. Decide which STYLE of bike you liked best (road, cross, hybrid, mountain, track, cruiser, etc.).
3. Buy the least expensive bike they have in that STYLE so long as it meets your needs, i.e., fits fenders, takes wide enough tires for the winter, etc.
4. Ride your new bike for a month or more without making any significant changes.
5. Start making notes of what you like/don't like about your bike.
6. Once you have those notes either start tinkering with components or start saving for a new bike.
It was my experience, as well as the experience of many others that I've talked to, that the first bikes we purchased din't really meet our needs.
Why? Because there is only so much you can learn from a short test ride. Until you put 500+ miles on the bike, you're not really going to know what it is that like or dislike about the bike or even if this was the right bike or style of bike for you.
I spent way too much money on an aluminum Hybrid as my first commuter bike that really didn't fit my needs. From there, I went to steel utility bike, to a steel "touring" bike to now finally a steel single speed commuter, which I love. I know that I could have spent 1/2 of what I did on that first hybrid and come to the same conclusion.
As far as seats/saddles are concerned, I've generally found that the more uncomfortable they look, the more confrotable they'll actually be over a long ride. It's not a truism, but not bad for a rule of thumb. As far as your joint in concerned, don't worry about it -- it's in no danger on a standard sadddle.
Best of luck this weekend.
When you make a decision let us know and post some pics.