Unlimited Data
If you upgrade to LTE, you will probably lose your unlimited data plan. My sister has unlimited data with Verizon, but was told that if she gets an LTE phone, she will lose it, unless she pays full price for the new phone. I had read this, also. So don't be surprised if you switch.
The typical, "because I personally don't use a device in this manner that must mean its stupid for *anyone* to use a device in that manner" post. You need to look beyond your one usage patterns and needs. It's very clear that there is a market for cellular models and there are many good reasons articulated in this thread as to why.
Mine is that I don't need cellular data on my iPad every month and so I like to get it when I travel. However, I don't want to give up the unlimited data on my iPhone just so that I can get a more expensive tethering/shared data plan--and I don't want to jailbreak my phone either. I don't even have LTE on my iPhone yet, its still on the pokey 3G anyway.
If you upgrade to LTE, you will probably lose your unlimited data plan. My sister has unlimited data with Verizon, but was told that if she gets an LTE phone, she will lose it, unless she pays full price for the new phone. I had read this, also. So don't be surprised if you switch.