  Recent scanning tunnelling microscopy (STM) studies on
Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi-2212) revealed the presence of severe
inhomogeneity with length scale $L_0 \approx \xi_0$, the coherence length.
Other studies have been interpreted in terms of mesoscale or nanoscale phase
segregation. Here we analyze heat capacity and NMR data on Bi-2212 and
(Y,Ca)Ba$_2$Cu$_3$O$_{7-\delta}$ and find no evidence for phase segregation or
gross inhomogeneity. For Bi-2212 the coherence scale $L_0$ increases with
doping from 5 to 17$\xi_0$ and the hole density inhomogeneity decreases from
0.028 to 0.005 holes/Cu. We conclude that STM measurements considerably
overstate the inhomogeneity in bulk Bi-2212.
