bpmills, my advice - DON'T be without it - Get one!
I am new, also to RVing - but I'm NOT new to electricity. As caddojay stated above: "I have been surprised at the RV parks we stayed in that had electrical fluctuations. Some because of the incoming power grid spikes and some because of out of date wiring and plug problems(loose connections, blown or shorted plugs, loose panels). With the sophistication of the T.V.'s, microwaves, computers and everything else, the investment is necessary. Maybe some units will offer these as options in the future. Until then, spend the bucks for a post plug in style, or get one hard-wired."
I would like to tell you all - DON"T be surprised at the RV parks you encounter with electrical fluctuations or problems of any kind. In the older parks, as Jay said, the wiring will be older and connections looser. Couple this with the great probability that when they were built they were either self-wired or went to the lowest bidder. The last statement holds true with some of the newer parks as well.
About 5 years ago, I had the opportunity to bid on upgrading the electrical wiring for a 42-space RV park which was owned by a state university. My lowest possible bid was 4X higher than the lowest bid they received. Low bid got it and their entire bid was less than 1/2 of my material costs. This told me they were not correctly figuring the load, according to the minimum code requirements, for a safe, trouble-free and functional installation. Otherwise stated, when completed, the wiring was going to be of insufficient size for the RVs staying there.
So, when we park there and use our A/Cs, TVs, DVDs, DWs, etc... (gotta have 'em!) - there may be problems with voltage and current draw. You never know when you pull in to park, whether the wiring is correct or not; just because they are new, remodeled, 50A or 30A - they may not know whether their wiring is CORRECT or not. Be protected - just my opinion! <!-- / message --><!-- sig -->