I agree with WAC's choice of aircraft. We(my wife and I) own a Piper Cherokee Cruiser and both enjoy equally flying around in the little plane and we share all the running and maintenance costs.
Our costs are very similar to WAC's. We are at a capital city airport and our annuals would be in the region of a $1000 more than his, but our insurance is about $200 less.
Posts about corrosion are correct. There is constant attention to this at every annual to the tune of about $500 extra each time.
Our engine overhaul in 2011 was $32 000 including new mounts, fuel pump, carburettor, 4 new Lycoming cylinder kits(160hp) and the RAM STC for upgrade from 150hp to 160hp.
I cannot emphasize enough to any PA28-140 owner how worthwhile the upgrade to 160hp is at overhaul time at an insignificant increase in the cost for the reward of a huge improvement in rate of climb and a small improvement in TAS(now 110kts) and even fuel economy(32lph).