I had this unit for about 3 years before passing it on. It did its job, but it never really grew on me. The flaws were objectively pretty minor but crucial for me.
There are loads of bpm scale and rhytmical patterns and variations to boot, so I bet you don't need much more functions on any kind of music you play. The chass is small but handy to use, and the clip sturdy enough, so it's easy to use laying on the table or tucked into your waist belt. The plastic housing felt a bit iffy, but I didn't throw around my unit and doubt nobody will, so I guess it's OK for the price.
The deal killers for me were the electronic blip sound of the click it made, and the lack of volume control of the click. The first is very subjective, the second a crucial feature in my opinion. As a minor complaint, in my experience it did us the battery quite a lot. These three combined made me to pass it on.
Be aware of the negative points I've just made, and the DB-30 still might fit your bill perfectly. It's not a bad product and does work as intended, so with that price I don't judge it as a dud. The new owner of my unit has been happy with it, as far as I know. For a cheap portable metronome I can recommended it with a caution.
