So, after not having played IaMP in over a year, I am thinking of trying to get back into it. What are the changes in the year that I was absent? New caster? Different tiers? etc.. I'll be picking it up using a stick now, though. That might improve my execution, which used to suck pretty bad before when I played pad-amp.
The game itself hasn't changed, it's the same as it's been since 2005. There have been lots of new techniques and tactics discovered. There is a custom caster client with support for a million things including custom colors, player names, auto replay saving and naming, and spectate mode (watch a game without sniping it) as well as an improved training mode dummy that you can set with a large number of predefined actions.
The tiers have shifted a bit and generally people agree with this list now:
A Tier: o 56.5 - Marisa Kirisame, o 55.0 - Sakuya Izayoi
B Tier: o 52.5 - Alice Margatroid, o 52.0 - Remilia Scarlet, o 51.0 - Yukari Yakumo, o 50.5 - Suika Ibuki
C Tier: o 49.0 - Reimu Hakurei, o 48.5 - Youmu Konpaku, o 48.0 - Yuyuko Saigyouji
D Tier: o 46.0 - Patchouli Knowledge, o 42.0 - Hong Meirin
Specific matchup information is on the FAQ page of IaMPWiki.