I have used a similar arrangement for transferring photos from Canon A530 to Nokia N800, using Nokia 770 as host and running gphoto2 to transfer the files. (You may remember the abysmal performance of N8x0 in trying to run gphoto2.) For your purpose as well, there would be advantages in using the 770, notably:

1. You can buy non-WSOD Nokia 770 for about $55 (three recent auctions on eBay).
2. 770 does not automount, and it will therefore not attempt to mount devices and partitions that you would prefer it to leave alone. (Undisciplined automounting is one cause of the problems with gphoto2 on N8x0.)
3. Lack of internal power connection to the USB transceiver is actually an advantage if you are going to use power injection in any case. This isolation protects the host from fluctuations in the USB voltage line and ESPECIALLY from static buildup in the "ground" circuits. (Static buildup is possibly the biggest problem for camera connection to N800 host, i.e. not using 770. This varies in importance from one camera to another. With one of my cameras, the N800 is practically useless unless it has a genuine ground connection, whereas the other camera gives less trouble. It may be significant that the more sophisticated camera is the one that needs proper grounding. No doubt other gadgets also vary widely in the extent to which they create static buildup that could affect a USB host.)

The disadvantages of the 770 as host are:

1. The low-speed bus. This should not be a problem unless you want to play video via real-time USB transfer.
2. The need for a USB gender-changer and the poor quality of the few that are available. I have found that most problems with host mode on the 770 can be traced to sloppy receptacles on the gender-changer.

There is a prevalent myth that host mode on the 770 is difficult and mysterious, requiring use of the flasher utility. I hope that an earlier post in this thread has helped to dispel that myth. (Use of a USB keyboard could lead to problems if you activated host mode without the flasher. Those problems are avoidable.)

ADDENDUM 1, Feb 24: I don't want to pretend that grounding the USB cable is a workaround for the bug reported in https://bugs.maemo.org/show_bug.cgi?id=3281 . The ground connection seemed to improve things somewhat for a while, that is all. The unfortunate fact is that you can't rely on N8x0 as a USB host for many devices beyond the basic HID and Mass Storage. Nokia 770 is a better choice.

ADDENDUM 2: Nokia 770 has its own strangeness as host in this setup. After the N800 was plugged in, the 770's dmesg offered all three partitions of the N800's internal card as candidates for mounting (sda1, sda2, and sda3). From past experience with multiple Mass Storage drives plugged into a hub, I expected to see the external card offered as sdb1, but nothing came up.

P.S. 770 will also run the 0xFFFF flasher to update N8x0's rootfs without disturbing a customized initfs.