I don't know if anyone else plays them regularly, but somehow this feels like it should have its own thread instead of which game are you playing.
I just finished Tsukihime and it was pretty good overall, though it didn't quite blow me away. I'd say that I liked the routes in this order: Arcueid > Hisui > Kohaku > Ciel > Akiha. The very beginning and very end of it was most interesting and it was a little unbalanced in that way, but only in a very very minor way. Overall I really liked it. The art looks more than a little amateurish, but the main sprites are actually really cute. It's a rare VN where the CGs look worse than the normal game art. What's nice about the art in Tsukihime is that all the character sprites are very expressive; they encapsulate the moods of the characters with so much spirit. My favorite is Hisui's AGNRYFAEC.
However, now, I'm playing Hanahira!, which might just be generic yuri (which I have no problem with), but I'm playing it... in Japanese! Many people have said that it's a good VN to read as your first one untranslated, because all the characters are lolis and thus the kanji level is absurdly slow. I'm reading the light novel of Welcome to the NHK! untranslated along with this and they're two nice steps towards making the full leap away from translations.