Personally, I haven't really encountered any major problems- I'll note a few which have happened top other people though.
Friday's Pre-registration line was atrocious. I'll just recap for a moment and not I got regular registration because I'm always waiting for the day I can spite the pre-registration-ers by taking less time. I went in the line at 9:55am and came out around 10:45 which wasn't bad at all. My allies in the pre registration line waited until 12:30/1 pm to get through. I feel as if these people prepared enough for the convention that they deserve a faster moving line. I remember the line at 2pm stretched all the way to the other end of the skywalk (where the hyatt is). I came back at 4:30pm to find it all gone- so something must have happened during that time period to as least alleviate the line. I hope this problem is fixed for next year. Every event has some glitches, and that line was certainly terrible- but I hope they improve logistics for it next year.
I didn't attend too many panels during the weekend, but I'll note that the capacity of the rooms for large events was infinite. The Aya Hirano concert had a line that spanned across the convention center out onto the skywalk above/outside of the fountain area and further but by the time we all got inside there was still some rows of extra space! I heavily underestimated the size/capacity of that room! Always ask about the capacity of a room- because Otakon can handle a lot of people!
I really enjoy the ability to use the floor across from the fountain area for dancing. One of the highlights of my con experience is actually what attendees bring to the convention: dancing of all kinds ranging from breakdancing, shuffling, to para para! It's wonderful seeing what random people from different places around the nation (possibly world) can bring to Otakon.
A note on security: They're trying their best to do their job and it took a while for me to realize that. I'll ask: if you were asked for a badge in order to exit the convention and didn't have one- how did you enter? If they do it at the main doors I feel like it's not fair because people who still need badges are mulling around... but just keep the badge on you at all times. I know we had one situation where my friend left her badge by accident with a group of friends in the con center to pick something up quickly from my hotel. I'm so glad we were stopped before exiting the convention asking where our badge was because otherwise we wouldn't have been able to enter! It's possible that's what they wanted to make sure of too. At least have a decent excuse at hand where you haven't registered yet (and let it be true) and forgot your money/ID in your hotel.
All this being said- Otakon is a place I return to year after year. The people I meet there have similarities and differences that I can enjoy. The setting provides for an open atmosphere where I can meet people and just have fun. I rarely have the chance to enjoy something like that. I'm glad Otakon provides enough 'venue' to attract people from all over~