Interesting question.
If you rightclick and bring up the properties of a drive, that uber-quick pie chart works by querying NTFS metadata structures which always maintain a "free space" counter. There's no count of files or folders in that case, only used and free space.
However, it looks like kernel32!FindFirstFile is indeed used when you interrogate a specific folder, or at least that breakpoint is hit as soon as I click folder "properties" while the machine is under a debugger:
kd> kL
ChildEBP RetAddr
00e8ed40 7cb12454 kernel32!FindFirstFileW
00e8ed5c 7cb13d59 SHELL32!HIDA_FillFindData+0x3b
00e8f1a0 7cb158c3 SHELL32!InitCommonPrsht+0x76
00e8fb70 7cac2ef5 SHELL32!FileSystem_AddPages+0x6e
00e8fb84 7ca7917a SHELL32!CShellExecMenu::AddPages+0x14
00e8fbac 7ca795b2 SHELL32!DCA_AppendClassSheetInfo+0x78
00e8fcc8 7cad5dd2 SHELL32!SHOpenPropSheetW+0x131
00e8ff3c 7ca9071c SHELL32!CFSFolder::_PropertiesThread+0xba
00e8ff50 77f76f42 SHELL32!_PropSheetThreadProc+0x18
00e8ffb4 7c80b683 SHLWAPI!WrapperThreadProc+0x94
00e8ffec 00000000 kernel32!BaseThreadStart+0x37
kd> bl
0 e 7c8137d9 0001 (0001) kernel32!FindFirstFileA
1 e 7c80eee1 0001 (0001) kernel32!FindFirstFileW
kd> !process -1 0
PROCESS 864ab4e0 SessionId: 0 Cid: 0568 Peb: 7ffde000 ParentCid: 0534
DirBase: 0e90d000 ObjectTable: e17822b0 HandleCount: 401.
Image: explorer.exe
If your code is substantially slower, maybe it's just a matter of optimisation. Are you doing this in native code or .Net? Can you post a snippet around your FindFirst/FindNext loop? (or link from pastebin.com)