I've tested BootMii beta1with the results as follows:
Transcend 16GB SDHC @ beta1: bootmii/boot2 hang in some kind of infinite loop
no brand 4GB SDHC @ beta1: bootmii/boot2 flash drive LED and skip it
no brand 1GB SD @ beta1: workable
I always plug Transcend 16GB SDHC in my Wii except maintainance to prevent contacts wearing if frequently plug/unplug, so I gave up beta1. Now I try beta2 with the following reault:
Transcend 16GB SDHC @ beta2: bootmii/boot2 flash drive LED and skip it with longer timeout (acceptable)
no brand 4GB SDHC @ beta2: bootmii/boot2 flash drive LED and skip it (seems faster than beta1)
no brand 1GB SD @ beta2: faster loading and workable except NAND backup failure as other topic
Finally I try to mix beta2 and beta1. I use bootmii/boot2 from beta2, so that it could skip but not hang if Transcend 16Gb plugged. And I use armboot.bin and ppcboot.elf from beta1 in 1GB SD to successfully backup NAND. Anyone that encounters incompatible NAND backup in beta2 may try this.
Still I have one a few question to the developers. Do the software interfaces keep unchanged between armboot.bin and ppcboot.elf from beta1 to beta2? And does the SDIO driver reside in armboot.bin and the FAT driver reside in ppcboot.elf? If yes, I guess I may mix armboot.bin from beta2 and ppcboot.elf from beta1 to improve SD performance.