Cathface, ooh goodness! I always forget that many of you live in the UK or Canada! Sorry about that! In that case, I can't voice my opinion. For those in the US or in an area where they can get the brands I listed, they are high quality ingredients, very healthy, and not much more expensive than Milk Bones.
My dislike of Milk Bones came along with my dogs. I became a huge dog enthusiast. I'm extremely picky about the quality of the food my dogs and small animal ingest. Purina, Beneful, Pedigree, Iams, Eukanuba, Old Roy... There are all very crappy foods (although some of those brands are starting to come out with better formulas because more and more people are turning their noses away from their lower quality products). Anything found in a grocery store, no matter where you live, is likely to be lower quality.
Milk Bones aren't going to kill a hamster or a dog, but the reason I don't trust them is because they don't even tell you what kind of meat meal they use in the ingredients. Overall the meat and bone meal advertised in these products is just a low-cost ingredient.
California Natural biscuits are made up of Lamb Meal, Rice, Oatmeal, Rolled Oats...
Compared to Milk Bones Wheat Flour, Wheat Bran, Meat and Bone Meal, Milk, Wheat Germ, Beef Fat, Salt.
When looking for dog biscuits, avoid cane molasses. That's the one ingredient that quite a few dog biscuits have (I went through my list and all but California Natural and some Nutro Ultra biscuits are without cane molasses in the ingredients). I have dwarf hamsters so I try not to feed them anything with cane molasses (it's surprising how many hamster foods here have cane molasses in them!).
Nutro Ultra Biscuits: Whole brown rice, ground rice, oatmeal, whole oats, chicken meal, pumpkin, flaxseed, lamb meal, salmon meal, chicken fat (preserved with mixed tocopherols), oat fiber, dried plain beet fiber, sunflower oil (preserved with mixed tocopherols), egg, natural flavors, inulin, tomato pomace, dried blueberry, dried pumpkin, dried pomegranate, dried spinach, dried carrot, dried cranberry, preserved with mixed tocopherols.
The Nutro Ultra biscuits seem to have the most quality meats, fruits, and veggies.
Maybe that info can help someone in the US.
Anyway, there is nothing wrong with Milk Bone biscuits for your hamsters, or your dogs. Out of preference, I don't feed that particular brand. But there isn't anything in the ingredients that would be harmful to your pets, and that's the main thing