For the most part, the Mango Update event for the day has gone smooth. While some have had to force the update out of hiding, the only major issue we've seen reported involves the LG Optimus 7 or E-900. It seems the Windows Phone is generating a 8018001e Error code during the update process.
There is a lengthy discussion going on over at Microsoft Answers but no real solution has been identified. It appears that during the jump from 7403 to 7720 the update fails and the error code is generated. There are a few who have made it to the 7720 update but failure occurs when the LG Update is applied.
Unfortunately, Microsoft hasn't identified a solution as of yet. For the LG E-900 users in the crowd, keep an eye on Microsoft's Troubleshooting Page for Windows Phones. If a solution is found for the 8018001e Error, it's sure to be posted there. We'll keep a watch on this one and if a solution is found, we'll pass it on.