Well the arcade units being sold now are more likely to be of the Jasper chipset (the chip less likely to RROD on you) because they are the systems with either 256 or 512MB of internal memory. It's only when you get an arcade unit that says it includes a 256MB memory card where it might not be a Jasper, but I'm sure that production run is long over.
Elites now could be Jaspers, or leftovers of the the previous model Falcons (which aren't as durable as the Jaspers)
You can tell for sure of the system being a Jasper by slightly stretching the little window of an Xbox box to see the production sticker and seeing a "12, 1A;5V" followed by what looks like Morse code.
Anything else, like 16.5V or 14.5V indicates the voltage rails or something and those correspond to the non-Jasper, i.e. RROD-imminent chipset varieties.
If value is a factor, you might want to splurge and go all-out for the Modern Warfare 2 bundle for just $100 more than the Elite. I think it is like a 99.9% lock that those limited edition consoles are Jasper units, and they also come with the MW2 game ($60), an extra controller (~$50) and a 250GB hard drive, which in Microsoft's eyes has a value of close to $200 by itself and isn't sold by itself yet.
