We will be going to Italy for a month departing on Sept. 28. We were reading in the Rick Steves book that he recommends the Firenze card. Yea or nay? How about the card for Roma? Thanks

Firenze card worked great for us.
It lasts 3 days, we stayed 3 days. It gives on child free entry per card, we were with 2 daughters.
It gives you faster access - and by God we skipped quite a few lines.
We went to a lot of museums.
So for us : time saver, money saver, handy and allowed us to see the Duomo when it was closed for non Firenze card holders.

Against its use is principally its cost - €72 is quite a lot for the number of museums you can realistically see in 72 hours but if you plan well and have children it becomes more economical.

Most museums on the list will have no queues at all but when you go to the ones that do, you'll think the card worth its weight in Medici gold.

And if you only have 72 hours, not having to queue is indeed very worthwhile.

[i didn't know that there are special hours for holders - that again increases its value and utility]

We are only going to be in Florence for one day. We are 3 adults. Will there still be very long lines in early/mid October? We mainly want to see Santa Croce, Accademia, and Uffizi. Any other recommendations?

With only one day in Florence, i'm not sure that I would want to spend the amount of time that is required for a worthwhile visit at the Uiffizi unless you are bog renaissance art buffs. [I'm happy to admit I'm not, but you may be of course]

Certainly the Academia, and Santa Croce, but also I would want to cross the Arno to "Altrarno", and walk up to San Miniato for the superb views over the city, and perhaps have lunch in a trattoria on that side of the city.

I would look at a few guide books and see what they suggest for "1 day in Florence" to give you an idea of what is, and isn't achievable.