Well, after playing through the game, in multiple story lines using EvoSpace?s walkthrough, it really seems to be that the anime is meant to go nowhere beyond where it did go. With Ciel disappearing in the end and Arc dieing at the end (unless her fading away relates to the ending in the game were she lived, but wanted Shiki?s blood so much that she went into a permanent sleep), it doesn?t seem like the series was given anywhere to go (not to mention that the references to Ren?s visit to Shiki are replaced with a weird scene of Shiki having a dream about Arc wanting to suck his blood).
1. No explainations... I mean they kind of touched about Hisui and Kohaku, and mention a few things about Nero Chaos (he was way more important in the game then in the anime). Also they leave many things out (because I haven't played Tsukihime I don't know which storyline they followed...) like Satsuki turning into a vampire.
The obvious story line is Arc?s. Satsuki becoming a vampire only happens in the Ciel story line (from what I can tell), and if she died, she wouldn?t be able to be a character in Melty Blood ReACT. Yes, they did leave out a sickening amount of information on Nero Chaos. It is also a kicker that Hisui and Kohaku aren?t explained in more depth. The only character that had her story properly told was Akiha, and the modifications to fit her into the Arc story line worked out extremely well I think. (the fact that Shiki actually got to go to the carnival and that everyone met, it also showed the part of Akiha from the game that wanted to be close to Shiki.)
2.Wasted time. This anime was extremely slow with the most of it told in flashbacks etc... Which wasn't that bad but it would have been helpfull with some explainations or more storyline parts earlier in the series.
I don?t believe this is true, the way the plot was presented was perfect, in that is forced you to keep watching each episode to learn more (the weeks between episodes drove me up the wall because I hadn?t really played the game).
3. Character Development. This is one of the things I think they did very well. They didn't really explain the characters background, but instead they showed it (which was pretty cool but left the viewer to guess alot of things). Also personally I like how they showed resentment and distrust between characters that left Shiki "out of the loop", although they should of explained some of it before the last few episodes...
Shiki?s personality is a bit cocked in the anime, as we don?t get to see his easy going nature quite as much. Arc?s feelings are also much different in the beginning of the game after Shiki kills her (she?s pretty happy to have tracked him down, and she?s impressed by him, not pissed at him and wanting him to suffer).
Multiple storylines would have been very cool and could possibly be used in a "sequel" (or maybe a movie/ova). Maybe due to the popularity of Tsukihime they will release ovas that could occur in a "alternate" universe and either tell other storylines in Tsukihime, or possibly (hopefully) stories from the plus disk or Kagetsu Tohya. I know many fans want this so it may come true. After all I'm sure no one expected a Tsukihime anime, well until it was announced that is.
The games seem to take care of the alternate universes quite well, apparently (like the alternate extension to Akiha?s true ending, where Shiki is alive). I?d personally like to see Ren?s story told in a short OVA, and then to see a Melty Blood series, which could easily be one full session with the added characters and story line (it?d also make for a kick ass action anime). It will be interesting to see how ReACT will affect Melty Blood?s story line, as it is an expansion, and not a sequel.