I have a lower end pc (it's about 6-7 years old). Before I upgraded some hardware, I would be fortunate enough to get 10 fps (it was unplayable without optifine). Now I get a solid 20-55 fps. But if there's lots of mobs on screen, or if I log into a server that has a massive spawn point with lots of blocks being used, it plummets back down to 10 fps again.
i seriously doubt the 1000FPS things. you could only get that with like a $2000 custom built computer. and even then you'd only get like... 700. and especially that 3500 FPS. that's kind of impossible... but anyway, back on topic.
I usually get around 60 frames with max settings. with 100 on max in 1.3.2. BLOW UP ALL TEH VILLAGES!!!