My first con was a much larger con (Fanime in 2003, to be exact), and while I wasn't miserable... I could have been happier.
Kumoricon last year was my second con, and in comparison, I had an absolute blast. Because it's only in its second year (I assume this is at least a large part of the reason), it's a much smaller con. While this means you're less likely to come across totally random cosplayers who cosplay characters that aren't as well known as the leads of the series (I think the majority of people were leads or secondaries, and there were five lesser-known characters from any given series, total. Correct me if I'm wrong, I'm just going on what I know and saw and cosplayed myself =D;), the atmosphere is a lot friendlier, like a big gathering of friends. I don't remember the names of 95% of the people I met at KumoriCon, but I'm positive I met and struck up a conversation (for at least two sentences) with 75% of the people there.
That said, get a room as soon as possible—either with friends or people you know (advisable; you can split the cost easier that way =D), or just for yourself. Make sure a responsible person who doesn't procrastinate is put in charge of getting the reservation made. There are always going to be people who are walking the halls into the night (I did last year; it's just more fun that way =D) or trying to find a way and place to crash because they don't HAVE a room, but that's mighty illegal (at least the latter is). The sooner you can secure the room, the better; you're more likely to not run into the "oh sorry, we're booked solid =D" problem that happens from having a) something going on in the hotel, and b) having that something happening on a weekend where people have Monday off from work/school. If you procrastinate, I warn you thus: If you don't have your room a month before the time you need it, you're going to have trouble. The sooner, the better ^^