Is it worth buying a RFLKT+ or is the RFLKT good enough? Looking at Amazon, the Wahoo RFLKT is half the price of the Wahoo RFLKT+. What practical benefits would I actually miss out on if I just went with the Wahoo RFLKT? Any pros and cons of the two different models?
I have a RFLKT+ which I use with Cyclemeter. The significant differences are the altimeter and the ANT+ bridge. The reason why I bought it was so that I could use ANT+ sensors, specifically the Garmin magnet less speed and cadence sensors. The altimeter seems to be very sensitive and enables more or less real time grade display – just in case you want to know why you're miserable climbing a hill :-) 

If you don't need those features, then I don't think there is a reason to by the plus version.

One other thing that I'd add is that the connection to ANT+ sensors is not as robust as I'd like. I find that I have to pay attention to the sequence in which I wake up the sensors and start the app to ensure that everything works. It seems like the sensor discovery process can take quite a while (maybe as much as a minute) which adds to the aggravation.

I'm not sure if this is a RFLKT+ thing, an ANT+ bridge thing, a Garmin thing, or a Cyclemeter thing… But if the fiddling with hardware and software isn't your thing this would be another reason to lean towards the RFLKT (the Bluetooth link seems much more robust).