I'd definitely take a look around in your local bike shop at some new offerings.
I know in my local bike shop, they sell brand new Trek bikes at prices a bit higher than the retail prices I see listed on the Trek website, and still have quite a few really nice bikes suitable for general recreational use in the $300 price range.
Another question I didn't think to ask before was what distances you have in mind.
There's a whole class of bikes designed for comfortable riding for people who will primarily ride them shorter distances, such as around 10 miles or less. These often include shock absorbers built into the bike seat mount, etc. They even look slick. And since they're new, they feature limited lifetime warranties.
Having said that, however, if you can find a decent deal on a bike you like used and in good condition for quite a bit less, then feel free to go for it.
Since you seem most interested in riding for recreation and fitness than for some specific aim (such as racing, touring, or scaling mountains, for example), the type of bike is probably less important than making sure the bike is the right size for you.
I've been riding a friend's spare bike for a while now, but it's got a 21" frame. I'm a tall guy (6'3"), so while I'm able to ride his bike and get decent exercise from it, a 26" bike frame is a better fit for me.
If you can hop on a few bikes before buying one, you might find out a few preferences. Some bikes feature flat handlebars, and others have curved handebars. For recreational riding, I vastly prefer flat handlebars. You might prefer one style over the other.
It looks like you may be able to actually try out the bike you're looking at before buying it, if I read your original post correctly. If so, that may provide all your answers. Upon close inspection, you might actually get a really good or really bad feeling about the whole deal.
let me know and i can pm a link to the auction if you want to check it out.
