Yesterday Appleto OS X Lion, but people who expected the first update to bring about major changes or fixes to problems that developed with the initial release of the OS may have to wait for a future release. The update is a relatively small one, at around 17MB for some people when downloaded through Software Updaate, but around 80MB as a standalone updater. For now the updater is just a minor bugfix that addresses some of the issues people have had with Lion, and enhanced fixes will likely come with the more hyped 10.7.2 update, which was mentioned as being in development before the 10.7.1 update was even discussed or released.
The updater file contains updated graphics drivers and disk handling tools like the disk image mounter and file server core services. It also includes an update to iChat and some of its system components like the quicklook and spotlight plug-ins for the program.
While the update does contain a number of new graphics drivers for all supported chipsets (Intel, Nvidia, and ATI), unfortunately one of the prominent issues of MacBook systems waking to black screens does not seem to have been fixed. The problem has changed for some users to show a direct kernel panic instead of merely the black screen, but for others the black screen still happens as it always did. If this update was to address this issue, then it may suggest the problems could be based in hardware. Some users who have had this issue have noted it no longer appeared when they've had their system's logic boards replaced.
If this problem persists for your system, then your best bet for now is to use the utility gfxCardStatus to prevent your system from switching GPUs, which appears to be a root cause for the problem. You might also try using a general maintenance tool like OnyX (Lion version) or Lion Cache Cleaner to clear the boot caches and force the system to refresh them based off of the new Kext files that have been included with the latest OS update.
Besides graphics, an ongoing issue with Lion that still is not resolved is Wi-Fi connections being dropped (see here, here, and here) when waking from sleep. Users will wake their systems and the Wi-Fi signal will suddenly disappear, resulting in network programs claiming you are not connected to the Internet. While for some people with this problem the signal will come back, for others it appears to drop continually for a while after waking. The updater package does not contain any Wi-Fi related updates, so it is unexpected that this behavior should change.
If you are experiencing Wi-Fi dropouts, a couple of things you can try to clear the issue is to reset the system's PRAM or SMC, and also create a new Location in the network system preferences that only contains a Wi-Fi configuration and no other ports (Ethernet, Bluetooth, Firewire, etc.).
The last issue that does not seem to be addressed is poor battery life in some of Apple's laptop systems. Some people have claimed that their batteries have diminished to less than half their original operating times after upgrading to Lion. While changes in power handling are expected with any update or upgrade, batteries should not change this drastically. As with Wi-Fi issues, very little of the 10.7.1 update appears to be to any system services and features that might be adversely affecting battery life. Your best bet for now if you are experiencing diminished battery life is to try resetting your computer's SMC, calibrating your battery, disabling unneeded system services like Wi-Fi, Bluetooth, and sharing services in addition to running your system on integrated graphics if needed (set this in the Energy saver system preferences, or use the utility gfxCardStatus to manually switch).