Mixed feelings greet on-the-go Net access

Nowadays, you can surf the Web and dash off an e-mail from a speeding train or airborne jet, as wireless service is increasingly available. Last week, Alaska Airlines joined such carriers as Delta, Virgin America, American and AirTran in offering in-flight Wi-Fi, putting the service on six of its jets with plans to offer it fleetwide by the end of the year. Since March, Amtrak's high-speed Acela trains from Washington, D.C., to Boston have provided wireless Internet access. Amtrak plans to add the service to routes in the Northwest and California in 2011. But what many business travelers see as a perk, others consider a potential nuisance that threatens to take away one of the last remaining respites from work.