Since it's been awhile, i'll entertain the pilots with some more questions
1) In your opinion, is the hub & spoke system advantageous compared to the Southwest model?
For an International Carrier like United that needs feed, yes the hub and spoke system works better than point to point SWA uses. They don't have to fill wide body aircraft.
2) Continuing on, are Southwest pilots based in a few different domiciles or are they more spread out (I know this is a United Q&A but just wondering)
They have pilot hubs just like United. United has 9 pilot hubs around the country. I think SWA has 8 when I count them up.
3) Have any of you been interested in piloting helicopters?
Not really, but maybe a seaplane someday.
4) When you retire @ United, do you plan to stop flying for good? Or, will you continue to do GA or Corporate Biz Jet trips?
When I retire I will retire. I might fly my own plane if I won a Cirrus or something for fun, but not a job flying for anyone. Otherwise why retire? 
Not a question, but I was flying 4/3/12 last year into DEN on United when a plane had an emergency landing (smoke in the cockpit) Props to the United crew who kept us informed throughout the 1-2 hr holding ^ also I was stranded in DEN that night (Tornadoes in Dallas) and United paid for my hotel even though it was due to weather and got me on the first flight out the next morning.
We can complain about management and the executives, but it is really the pilots, FAs, and GA's that do a great job and a reason why 90% of my flights are on UA.