Here we are, a few days before the consumer release of Vista, and people are already speculating when SP1, codename Fiji, will be out. Like most, they feel that the time to upgrade would be after SP1 is released. I guess the idea is to let all the early adopters shake out the problems, then pick up the improved version later in the year.
Probably not a bad plan if you look at the past. Windows XP SP1 came out after 11 months, and there are always a large number of defects found early on – some are minor nuisances, some are major security issues. I guess it depends on your tolerance for risk and need for the newest OS. Besides, if you wait you will have access to all the tips and tricks that those early adopters have documented.
Current predictions are that an SP1 version will be out before the end of the year. If that is the case, there is no real reason to pick it up immediately. On the surface Vista seems more of a evolutionary type of change anyway, so consumers can afford to be patient.