No answer for you but i thoguht i would make feel better by saying i have a very similar issue. I only switched on home sharing on the iPad yesterday for the first time and i believe it was working all ok. I believe I saw the artists and albums and songs all listed. I remember searching for 'Any Winehouse' on the iPad and her albums appeared ok on the iPad. I was then able to drill down into those albums and them play them on the iPad. i thought this was an amazing feature of PC iTunes to iPad integration. What with all the Apple bashing and the iOS6 map issue that has been going on in the last few day i emailed a mate to rant about how great this feature was. My point to him was that is not a revolutionary idea but that the Apple softway is very slick and works well. Maybe my comments wer a bit premature.
Anyway today I opened the iPad and tried to do the same thing. Only a few artists appeared so i am not able to easily find the albums and therefor songs to play. The songs are all listed but only a few of the artists are shown.
I have checked iTunes on the PC and all the artists are there and i can list them correctly. I had thought that maybe there was somethign wrong with my album tagging but this is all ok. I was able to search for an artists on the PC iTunes and they appeared ok. I could find that albums on the iPad but only if i knew the album name. About a dozen artists do appear on my iPad but this is only a fraction of my library so really is not much use.
I am using iOS 6 on all devices too with the latest iTunes on the PC.
I have tried rebooting both the PC and the ipad but this made no difference.
I also tried switching off home sharing on the ipad and back on again in the hope that this migth also help.
Not wanting to waste all of my Sunday mornign I have no decided to give up on this feature.
Its a real pity as this is a top feature of using iTunes in the house and playing our music library on any device.
If it dont work then it is ally a big let down.
Lets hope it is a buglet with Itunes and that it can be fixed soon with a PC iTunes update.