Using this sketch::

include <stdio.h>

void setup() {
Serial.begin(19200);
}

void loop() {
char string[40];

string[0]=0;
sprintf(string,"Characters: %c %c", 'a',65);
Serial.println(string);

string[0]=0;
sprintf(string,"Decimals: %d %ld", 1977, 650000L);
Serial.println(string);

string[0]=0;
sprintf(string,"%s", "A string");
Serial.println(string);

string[0]=0;
sprintf(string,"floats: %4.2f %+.0e %E",3.1416, 3.1416, 3.1416);
Serial.println(string);

delay(1000);
}

Results in this output;

Characters: a A
Decimals: 1977 650000
A string
floats: %.2f %.0e %E

As you can see, the sprintf function is working for %d, %s, %c but not %f

Using latest github version, downloaded today (april 16th)