Good morning! I'm having the exact same problems listed here, using a 27" iMac (2011/Thunderbolt), running Lion 10.7.1, and the problem occurs whether I'm connecting via AirPort/WiFi or Ethernet. This problem also occurs whether I'm using a new 3TB Time Capsule, or a first-generation 500GB Time Capsule.
It will typically take anywhere near 5-10 seconds after waking up from sleep before an internet connection sets up; however in some cases, it can take about a minute. The latter seems to happen any time when a Time Machine backup is interrupted by the computer going to sleep (e.g., the computer is in the middle of a backup, and I am leaving home for whatever reason).
I've also noticed that the computer's clock seems to freeze while the machine is asleep - when I wake it up, it will show the time that it was when the iMac went to sleep, and will not update to the new time until it re-establishes its network connection.
I agree that there certainly seem to be a lot more teething issues present with Lion, in addition to its loss of core workflow functionality (expose and spaces) that has been present in over half a decade of Mac OS X releases. Overall a disappointment, and I too am considering a revert to Snow Leopard.
If anyone finds a solution to the problem of not being able to connect to the network after sleep - whether Ethernet or Wi-Fi - I would appreciate any insight you gain or anything you may learn.
cheers,
Mark
----------
I solved the problem by setting the monitor to go to sleep after a certain amount of time, but the computer set to never.
Unfortunately, that is not an acceptable solution - and my comment is directed at Apple, not you darster. While you've found a workaround that works for you - and I commend your creativity - clearly that doesn't work for a laptop, or even an iMac, as the end result is the computer is still running, active, and drawing power - even when I'm not home. Given the premium paid for Apple hardware, isn't acceptable product functionality.
regards,
Mark