Just because someone is selling a bike, doesn't inherently mean that there is something wrong with it. Give me a full suspension over a hardtail any time -- especially when the bikes are at the same price point.

That said, obviously a FS bike requires more maintenance and maybe is not ideal for someone that is just getting into the sport.

The Specialized might not be(I don't think it is) a Stumpjumper. The 08 Stumpys came with Fox forks/shocks. Also, the "XC" on the toptube would suggest the FSR XC model -- the 2009 model came with a RS Tora fork and X-fusion rear shock.

The Scott is a 2012 model, so that would be at the top of my list. You shouldn't have to worry about suspension service right away with that one, but keep in mind, forks/shocks do require somewhat frequent maintenance if you want to prolong the parts life. I typically service my shocks once a year(or 1-1/2) and service my forks 2x a year.

I don't know much about Radon, but it does look to have the best component spec of the options.

Remember, if it's not a good fit, then it doesn't matter how good the deal is.