Run 3 companies.
1 is a software company. Yourcostcenter.com I travel a lot giving seminars, using the Air for emails, powerpoint, Ichat, (so I can stay in touch with the wife and kids) and use Netsuite (on Safari)for all company marketing, CRM and accounting. Use Firefox for all our programs behind the scenes controls.
2 is a commercial painting company. Use Excel, MYOB, Filemaker Pro.
3 is a Ballet School with my wife. Same software as above except Quickbooks. instead of MYOB.
Since Feb., I only use the Air. I have the SDD drive and have no issues whatso ever with room. Still have 29GB left.
Only issue I have is temp. case gets warm and fan kicks on alot. But in no way a deal breaker.