I also cracked my screen, and am convinced that the design leaves the LCD panel too susceptible to breaking-- mine fell from ~2 feet onto hardwood, and the screen should not have cracked.  For such an expensive remote, I feel it is unreasonably fragile.

Since Logitech only offers a discount on a replacement, stating they have no repair facility, the cost to fix it ($125) would be over half of what I paid ($195).

No repair option plus an official post on their forums stating "The Harmony One was never intended to be opened" got my goat-- expensive stuff should be repairable!
[Link: forums.logitech.com]

I had no problem dismantling my Harmony One-- anybody who has disassembled a cell phone or iPod can take it apart.  There are four screws (two visible, two under the sticker) under the battery compartment cover, then three underneath the soft plastic piece which can easily be pried off (it clips and is glued under the raised dot).  The top and bottom of the case can be pried off starting at the battery compartment, putting a spludger into the grooves and prying it until the clips release.  Inside, the touch screen ribbon connector (under clear tape) flips up to release the ribbon, and there are two screws holding the main board to the top of the case.  On the main board, the taped plastic light pipes (for the left/right and two bottom buttons) adjacent to the screen snap off with gently prying.

The TFT LCD itself has a 20-pin strip at the end of a flex PCB, soldered right to the main board.  I removed it with a soldering iron, using a solder sucker and solder wick.

I bought a broken remote on Ebay with a good screen, dismantled it, unsoldered its LCD panel ribbon, and soldered it back onto my original Harmony One-- works like a charm now.  Soldering it was tricky-- the ribbon ends get chewed up a bit when removing it, so I:
* sanded the mating side of the ribbon to expose more of the 20 leads,
* tinned the 20 pads on the PCB,
* taped the ribbon over the pads so the leads lined up wth the pads,
* lifted the ribbon with a toothpick to apply a tiny bit of flux to each pad,
* removed the toothpick so the ribbon leads dropped down to touch the flux,
* hit each tinned solder pad with the soldering iron, pressing down on the ribbon with a plastic spludger to affix each ribbon lead to each PCB pad.

I find it disturbing that:
1) The Harmony One is so fragile that its screen breaks easily,
2) No repair service is offered, instead only discounted replacement,
3) Logitech explicitly states that the Harmony One is not designed to be opened, when clearly it is straightforward to disassemble, repair, and reassemble.

This would have been much easier if the LCD panel were available aftermarket, in the same way iPod and iPhone screens are easily purchased for <$30, but the part is not available anywhere.  FWIW the TFT LCD panel (with ribbon) is manufactured by Foxconn and is marked "CT022TN05 V.6 M1-F".