Sofitel is a strange program, with lousy tangible benefits, and pretty good intangibles (IME). They recently changed the rules where standard members no longer receive free upgrades, but as a bog-standard member, you still get a free welcome cocktail, 4pm late checkout, and gym access. That's not bad, considering anyone can simply sign up for Sofitel's Privilege Program.
If there were more Sofitels in cities I travel to often, I would likely shoot for Privelege Gold (6,000EUR Spend or 14 Nights/yr). However, they simply don't have enough hotels to choose from, and other Accor brands (with the exception of Pullman Hotels) don't count towards Privilege Gold Status

.
The rewards program also stinks. 10EUR Spend = 80 Compliments Points. It takes 20,000 Compliments Points to redeem for a 200EUR Weekend Voucher Booklet. The vouchers are good at any Sofitel, Pullman, Novotel, Mercure, Suitehotel, Ibis, All Seasons, Etap Hotel, Formule 1 or Accor Thalassa Property for a Fri/Sat/Sun stay, and come in booklets of 4 50EUR Vouchers.
It takes 24,000 Compliments Points for a 200 EUR Voucher Booklet good any day of the week at any Accor property.
All compliments points expire two years from the end of the calendar year in which they were earned

.
I'm obviously not staying at Sofitels for the "loyalty" program. The excellent hotels, great beds, great service, and "soft benefits" have kept me coming back, though. They also tend to have hotels in some interesting locations (my stays to date have been at the Sofitel Florianopolis, Brazil & Queenstown, New Zealand). I'm planning to try out the Sofitel Cartagena for Thanksgiving. The chain has hooked me, and is definitely the first option I consider if I've already bagged my SPG Plat for the year. A shame they don't have more hotels to choose from...