While I don't know hardly any of the people playing the characters, a number of them are pretty darned good!
elgoose's Snape had a great opening line ("The heat hits him like an Unforgiveable..."). mcamy's Hermione, andsaca369's Narcissa, and manynames's Draco seemed nicely in character to me. mcsister's Lockhart was fun, and marksykins's Neville was cute.
maeglinyedi (as Voldemort) is one of the only two people I know, and he was great to see. nimori is playing Black, but if he already did his intro I missed it.
Trying to follow a RP on LJ is really rather odd (you need to keep going back and checking old posts for new comments), but so far it's worth the effort! Check it out if you haven't already!