I went to an IMAX showing of 300 last night.  Though we arrived in advance of the showing, the theatre was mostly full by the time we arrived so we ended up sitting in the second row.  In a normal movie theatre, the second row is considered a bit too close to the screen.  In an IMAX theatre, the second row is waaaaaay too close to the screen.

That having been said, the movie was a reasonably well done, though I found the sheer size of the screen and my closeness to it detracted from my enjoyment of it.  Oh, and people who do not like violent movies should refrain from viewing this movie as their sensibilities will very likely be offended.