I was an engineer at HomeAway during last year's IPO, and all employees were under a 6-month lockup period (during which time you can not sell stock, or enter into any sort of agreement with a third party regarding stock options).
As an employee, therefore, the IPO event itself is not too significant. Unless you have $1 options (or already own stock at a very favourable price), you can't bank on a return due to the uncertainty of the lockup period. Also, the end of the lockup period itself (although completely anticipated by the market) will likely be unfavourable for the stock price as selling employees introduce more supply.
The lock-up doesn't necessarily apply to people who got in at the IPO, such as during the roadshow period. Also pretty sure the lock-up doesn't apply to people who bought private shares in secondary markets, such as the Goldman clients who bought in when Goldman offered private stock about 6 months ago.