I stayed there this past weekend (Sheraton Petaluma). Bright, attractive, fairly new hotel.
Plusses - staff was quite nice. Rooms, while not exceptional, were decent, and the beds were in good repair. The HSIA, while not free, is $5 for a 24 hour period (not "noon-to-noon").
Minuses - the club lounge is closed on Friday night and through the weekend. Instead of a breakfast voucher, plats get a $10 f&b credit. If travelling alone, this will cover a continental in the dining room, but that's about it. Travelling w/2 going to cost you. Breakfast was of decent quality - the maple syrup really came from trees (and not a high fructose corn syrup factory), butter whipped, etc.
Location? You need to drive to go to the city center of Petaluma (not very far), which is a charming little place - I've lived in the Bay Area 20 years and never went to downtown Petaluma prior to Friday night. Had a fun wine tasting/small plates/dessert at Della Fattoria (open only at night on Fridays.)
Overall, I'd recommend the hotel if you need to stay in the area, or want a not-too-far place to start your day for Sonoma County wineries. I find it superior (but not as convenient) as the HHonors properties in the Santa Rosa area.