If I had to rate Dennou Coil according to its progression, it starts at around 6, then slows down to 5, then slowly builds up to 10 (climax) during the latter half, 10 being the highest. This show is quite underrated, mainly because people don't get past the first few episodes. I definitely recommend it.
Princess Mononoke is very good, with great art, imagination and premise. Whether you will like it or not will probably be decided by the plot and its brevity, but you should give it a try.
I've been meaning to watch the ARIA series, but I couldn't get past the first few episodes. Does it get much better? Why is it worth watching?