What can I expect to hear from a decent analog FM Tuner?

With FM you are at the mercy of the broadcaster. I listen every night to All Night Jazz on WUSF 89.7 Tampa. A good sounding station - but they use digital files. Not as good as the same music played back on my Marantz CD67. All the other commercial FM stations in my area broadcast musical dreck! So unless you have a college station nearby don't expect sonic delight from any analog tuner!

Just stream free Internet radio. You have a world of choices awaiting! 

A good FM tuner with a good antenna can sound every bit as good as a digital source. How close are you to the broadcast towers? Are there stations you like nearby that broadcast with a good signal? What are your options for antenna placement (a good roof mounted antenna is optimal)?

As far as how it will sound, yes, it can sound different.  That depends a lot on the tuner you choose.

Here are some places to get more info about tuners and reception - fmtunerinfo and fmfool

I have six vintage FM tuners. Including two tube units (Fisher and Scott), plus a McIntosh MR77 and a Marantz Model 23.