Rosberg's arrival carried a nostalgic dimension: his father, Keke Rosberg, had won the 1982 Formula One World Championship driving a Cosworth-engined Williams, and Nico was stepping into his first full season after claiming the GP2 Series title in 2005. Webber was entering his second year with the team.
The FW28 was the first Williams V8-powered car since the FW12 in 1988 following the new Formula One engine regulations that reduced displacement from 3.0 litres V10 to 2.4 litres V8. It was also the first Williams car on Bridgestone tyres since the FW22 in 2000.
Despite the effectiveness of the Cosworth engine in the new V8 formula, the FW28 suffered from a persistent handling problem on corner entry that undermined its competitiveness at most circuits. The team showed brief flashes of promise — at Bahrain, Rosberg scored points on his Formula One debut and set the race's fastest lap; at Sepang, both cars qualified on the second row before suffering engine failures — but poor reliability repeatedly negated positive performances.
Webber came closest to outright success in Australia, where he led at one point before a hydraulics failure ended his race. At Monaco an exhaust fire eliminated him again while running as a potential podium finisher. On lap 21 of the Australian Grand Prix, Webber became the first Australian to lead his home race since the last non-championship Australian Grand Prix was held in 1984 — a symbolic moment despite the ultimate retirement.
Williams finished eighth in the Constructors' Championship with a modest points tally. Dissatisfied with the reliability record, Webber departed at the end of the season to join Red Bull Racing. Rosberg remained with the team into 2007.
The FW28 retained the dark blue on white colour scheme from previous seasons but lost the stylised "kidney grille" nose design that had been associated with the BMW-era cars. Major sponsors included Allianz, RBS, FedEx, Reuters, Oris, Petrobras, and Castrol, with new partners Mobilecast and Tata Group joining, while Hewlett-Packard departed after their BMW-era contract ended. At European and German rounds the Budweiser logo was simplified to "Bud" due to licensing issues with parent company Anheuser-Busch; at French and Turkish rounds it was replaced entirely with SeaWorld branding.
Following the difficult 2006 season, Williams committed to Toyota engines for 2007. An interim variant designated the FW28B was built using the FW28 structure but fitted with Toyota's 2006 RVX-06 V8. The car was used in winter testing to allow the team to evaluate Toyota power and develop aerodynamic components — including revised front wing configurations — ahead of the FW29.