They don't smell as long as you clean the cage out regularly and properly.
They can bite if scared by being suddenly grabbed. If you're thinking of getting one, here's a few tips:
1. Put everything in the cage, if you don't want the hamster to chew the bars (which is predominantly a sign of boredom), give it plenty of things to run over and through.
2. When you've introduced the hamster to the cage, leave it alone for 2 days to allow it to get used to it's new surroundings, obviously you'd still check it's ok.
3. Allow it to get used to your scent by slowing introducing your hand into the cage, but don't pick it up just yet. Keep doing this quite a few times in the day (especially in the evening and night when they're more active)
4. If you have children who will want to to handle it too, teach them how to handle hamsters properly and gently.
5. Give them wooden shapes or them treat sticks you can buy to nibble on as this will help keep their teeth trimmed.
For more detailed help on how to care for a hamster go to this link:
http://www.hamstercare.co.uk