The short version: the more desirable the area is, the worse the traffic will be. Any time estimate Google pops out, quadruple it to get an idea of how long your commute will be on a bad day.
The long version:
During both rush hours, I-4 backs up near I-275 westbound and around I-75 eastbound. I-275 backs up eastbound around the Tampa end of the Howard Frankland Bridge and around downtown in both directions. Gandy Bridge backs up around the Tampa end. The Courtney Campbell Causeway is either smooth or a nightmare. Practically every east-west road to the west of Dale Mabry Hwy (Town 'n' Country/Westchase) or east of I-75 (Brandon/Mango/Seffner) is horrendous right now. The Veterans is always bad in peak direction during rush hour. To hell with traffic anywhere near the airport, especially Westshore. Northdale, Citrus Park and Carrollwood are nice, but a pain to get around. New Tampa traffic is much better now, but Tampa Palms and anything in Pasco County is still some of the worst. With the exception of Temple Terrace (where I live), most of the area not affected by the east-west snarl (between I-75 and I-275) is low income. Long story short, unless you like sitting in your car for hours Los Angeles style, avoid the St Pete/Clearwater commute.
If you're working downtown, try to live close to downtown (Downtown, Bayshore, or Hyde Park/South Howard, if you've got the $$$), close to the ends of the Selmon Expressway in South Westshore/Brandon/Riverview (something more affordable) or Temple Terrace (middle to low end). As mentioned, West Tampa, North Howard and Seminole Heights (old areas around downtown) are slowly becoming gentrified, presenting another option - but the keyword is "becoming" on that one, it's not quite there yet. If you want a bit of country bumpkin and don't mind a drive, there's a housing boom in progress along US41 through Gibsonton, Apollo Beach and Ruskin - caveat emptor, as the roads down there haven't been expanded yet and could become the next traffic snarl, plus there's plenty of freight train traffic along local roads and practically no public transit.
Transit can be a bear to use with HART and PSTA system funding being the way it is right now - if you intend on making use of transit, do your homework in advance.
Avoid living near any road that is 6+ lanes wide, as they will usually make your life miserable 7 days a week. This goes for any part of the Bay Area - our drivers are aggressive/bad, which will cause you to have many close calls/accidents if you aren't giving other drivers enough room to do something stupid. In other words, if you weren't a good defensive driver before moving to Tampa Bay, you will be by the time you leave.
Oh, and people forget how to drive when it rains.