Really depends what you are after. I have the 4660 Ultra for my main viewing because of the ethernet and the USB which I initially used as my beginner "media server". All my other rooms have Premieres and a RokuTv in the kitchen. If you are happy with the performance of your current device and don't need the extra speed and features the Ultra offers, then I would say no. If you want faster speed or you have a higher resolution TV that isnt supported by your current device, then yes. It depends on your setup and what you need or are after. It is a good buy at $80 which is the normal sale price, and $100 for regular pricing.
These devices go on sale from time to time (this is not a 1-time offer you are seeing). It may be another couple of months before the sale is on again, but it will be. I generally like to buy the devices in a store as opposed to online, but just personal preference. Figure it will be easier if I have to return for any reason.
To date, have yet to replace any of my devices, but have bought more of them for friends and family.