My 3 year old 1TB Western Digital WD10EVDS (I think that was the model) just died in my tivoHD last week.
I just bought this one:
Western Digital WD20EURS 2TB and got it working in my TivoHD (same as your model).
I just used winMFS and ended up getting 198 hours HD recording space. I know I sacrificed some of the drive space, but my family never even came close to filling up 157 hours of HD recording space, so getting bumped up to 198HD hours was just fine for me.
I had to use my *original* tivo drive to pull my image from. Even though the failing 1TB WD drive was still readable, and I was able to back it up, it still would make my tivo reboot over and over if I tried to put its image onto the new 2TB drive.
Long story short - success, but I lost all my season passes as my image on the original drive was 3 years old.
Also, I did NOT have to use wdidle3 with this drive. It boots, and soft-reboots just fine. No hanging.