I have an iPad3, with LTE. No regrets in spending the extra, perfect for on the train and sat at airports (I live in Plymouth, and my dad in Edinburgh so I spend a lot of time flying in between). Also saved me some over the summer when I moved into a new flat and had to wait six weeks for the interest to be turned on.
Like you I have WiFi at work and home, so do not use the data unless I am elsewhere.
I also love working in coffee shops, so it’s ideal in that situation as more often than not the WiFi in them is either rubbish, or just doesn’t work.
Only you can really make the decision about weather you need 3G/LTE though, personally I wouldn’t buy another without it.