As a mother I have tried it all, especially when it comes to finding a bath seat.  I tried several types before I found one that worked for me.  It seems like a simple concept of getting something to bathe your child in until he/she can sit up on their own... but it's not.

First, there is no such thing as a good multiple-stages bath seat.  These are the types that hold an infant in a lying down position and then can sit a 6+ month old in an upright position.  Some offer stages in between too.  They DO NOT work.  Common problems I have come across:  The bump that holds the infant's bottom will later be in your old baby's back (not comfortable); There is no type of grip where the older child sits, so they are constantly sliding around; The construction is poor and it may collapse (trapping your child's legs) at any time; In the older child position, it takes up a lot of room.  In my opinion, you just need to face facts that you will end up purchasing 2 seats.

For an infant seat, simple is best.  A brand new baby is not going to care if it has toys or pretty pictures on it.  Save your money for the years ahead.  Be sure, however, that the pad on the bottom does not become slippery when wet.  If it does, use a folded up towel.  I personally recommend the Primo Infant Bath Seat that you can get for about $10 retail.

When it comes to an older baby seat (~6 months or when baby can sit pretty much independently), the best thing on the market is the Safety 1st Tubside Bath Seat.  There are two types and it is important to get the correct one.  The first has suction cups that attach to the bottom of your tub.  If you have a textured tub as I do, THIS SEAT WILL NOT WORK.  I found out this piece of information the hard way.  The second has an arm on it that clamps to the side of your tub.  It works great if you have a textured tub because there is no suction needed, but it does not work if you have sliding shower doors.  I have learned that it is just as easy to leave the seat in the tub at all times than it is to take it out, get the water out of it, and find a place to store it.  If you plan to take it out, the fact that it wont work with sliding doors is irrelivent.

No matter what seat you choose, remember never to leave your baby unattended in the bath tub!