The Seydel Session Steel is simply excellent. It is airtight, responsive, and expressive. The closed covers give it a slightly warm tone. The comb is smooth on the mouth and the extended covers make it easy to get an airtight seal. It is a professional grade instrument, hand-made in Germany.
The two big advantages of stainless steel reeds:
1. they stay in tune better than brass
2. they do not corrode, rust, or form green gunk like brass
The stainless steel is really easy to keep clean, and they can even be rinsed out under running water.
The key of Low F# is extremely practical, being a half-step below G. I like to think of it as a "Gb". It is a nice alternative to the standard F#, which is very high. I use both equally, depending on the song and the type of sound I want.
It is very practical key when playing with guitarists who tune down a half step (playing Gb in first position, Db in second position, Ab in third position).