Why disappointing? Your dual-displays simply allow your Windows desktop to be larger. When you connect with RDC, your desktop will be resized to fit your Mac's display, possibly mitigating the need for two monitors to begin with.
Like some posters above, I RDC from my 24" iMac to my work computer (Windows XP with dual-19" displays). This effectively makes my work desktop 24" in size--my Mac's display gives me more than enough real estate given its larger size and resolution.
If you are looking to get dual displays for your Mac, you
may be able to span the RDC client across both displays, effectively doubling the width of the desktop on your remote computer--this may provide a "feels like work" experience, though I certainly hope your new Apple displays are better than the ones provided at the office! (I say
may because this "span" feature is available in the Windows RDP client, but I haven't verified it on a Mac).
Just keep in mind that an RDC connection ignores the display setup on the remote host--the RDC CLIENT running on your Mac determines the size of the desktop, not the physical hardware of your office computer.
Cheers,
VP