Actually, I'll take something of a contrary view here... With any device there can be hardware issues in the earliest builds that are fixed in future builds. Manufacturing issues can be identified and resolved (e.g., screen adhesion issues that cause yellow tints, a la iPads), problematic components can be fixed by suppliers (e.g., screens that suffer from inconsistencies, WiFi components that can't be completely fixed in software, etc.), and even components can be swapped out when they can't be fixed. This is why hardware has revision numbers just like software does.
This isn't specific to the SP3, nor even to consumer technology in general. Many people say that you shouldn't buy a car in its first model year because inevitably issues will be identified and fixed in subsequent model years. Automobile manufacturers handle the worst of these issues with recalls, of course, but then again their business model is different and cars are easier to fix compared to something like the SP3.
This isn't to say that you shouldn't buy the SP3 right now, if it offers something that you just can't live without. But I do believe that if you wait a few months, you're more likely to get a unit that doesn't suffer from some of the teething pains of the first units built. Or, make sure you get something like Microsoft Complete that will provide for relatively easy exchanges.