Well, we completed our one week stay (about a week ago) and I thought I'd follow this up.
The room types seem to be: Deluxe Room, Business Deluxe, Club Floor, Jr Suite, Presidential Suite.
We were booked on 18, the club floor, in a standard and nicely appointed room (SPG Gold on points). Though we didn't find out until the last day, you should know that on the Club Floor, bottled water is complimentary
They also gave us a very nice half bottle of Malbec on Day 1 and a torte of some sort (it was delicious) on Day 3.
This property may not be a St Regis but the staff there treated us as if it were. Always extremely pleasant and helpful. We really enjoyed our time talking with the staff, from the desk crews to the concierge to the doormen to the security guard!
I don't know how much nicer the rooms on the Club Floor were compared to the other floors - I know others have commented on rooms needing renovation. Ours was just fine - at a 4 Star USA level. The Club Floor guests also get free pool/health club access. I'm not sure of the cost for others. Truthfully, we never made it up there all week as we were too busy enjoying BsA!
Be aware that Internet Access in your room is 50 Pesos/day - a bit steep (~ $17USD) - but you can access the Internet from the Business Center for 5 pesos per half hour (on their computers or you can bring your laptop). You can only do 24 hour blocks from your room. Also- they have this ingenious service where they'll give you a cell phone free. The catch, as there must be, is that calls made are charged as if you were in your room. That's never good ;-) I bought a SIM card for 50 pesos that included 20 pesos of airtime on Personal. Outgoing calls were 1 peso local, 1.5 pesos to the USA, incoming calls free (as is common outside the States).
Location: Perhaps it depends on who you are and what you like. We saw the location of the Park Tower and while not bad, it was simply not as "in the action" as the Libertador. Yes, I am sure it is many levels of posh-ness above the Libertador, but we loved walking right out the door one block to Florida Street and right into the action! We are "young-ish" and we like convenience and things at our doorstep so YMMV. We prefer that to jumping in a cab everywhere even if the cabs are only USD$2-3 per trip
Summary: The Sheraton Libertador is a very nice hotel in a great city. The staff here, with very few exceptions, will bend over backwards for you. The location is prime. As a Gold or better I'd think you're likely to be upgraded pending availability without problem. While I'd be tempted to try a night or two at the PT on a future trip to compare, we'd absolutely be happy booking back into the Libertador, especially given the difference in *points. If any staff are reading this, thanks for helping us have a very nice and memorable trip to BsA.