so since I saw people discussing FPS and shadows and lag or what-not, I decided to do something myself to see how my computer performed.
229993 bricks 
(the map was a recreation of slopes that Treynolds416 made with a script, and yes you read that right 229k bricks)
max view distance 
no shadows:    60 FPS
minimum:        60 FPS
low:                 60 FPS
medium:          60 FPS
high:               50-57 FPS
on very high/max, no shadows appeared at all .. weird.
keep in mind this was all in single player.