I get great 4g signal inside most buildings around here, I was browsing full speed in the middle of a Sam's Club yesterday, so I dunno. Cities that are LTE are still fairly spotty though at this point, and if you're on the fringe, you'll of course lose it once you step inside. But I still tend to have enough to browse.
But yes, very few Android smartphones are gonna last more than a day, and none give you a solid two days if you actually use it. Blackberries and iPhones last that long because the OS runs a single hardware configuration, and both can be heavily optimized for each other. Unfortunately that's just the price you pay for choice, but its more than worth it in my opinion.
LTE phones will use even more battery than most at this point, as the LTE radio is completely separate from the other radios, and hasn't been around long enough to be optimized. There's also the issue of the network itself being young, and further revisions to the networks and LTE PRL's will reduce the amount of signal boosting needed by the phone, improving battery life on current devices.
But my Droid Charge gets me through the day just fine, and I use a good bit of LTE, and its overclocked to 1.2ghz. Sure, I still have to be a bit careful with it, and I keep data off when I'm not using it. But if you're not planning on downloading alot of things AND talking on the phone an hour or more total each day, you should be fine.
As others have said, the Charge is by far the best of the currently available LTE phones. I love mine, and would recommend you get one as well to make sure you're locked in to unlimited LTE. If you just can't stand it, you can always sell it and get something else full retail. But there's no guarantee you'll be grandfathered in if you just buy a phone off ebay, since you would never have signed a contract with them. But the SGS2 will likely be the better phone for enthusiasts such as ourselves, due to the great screen and massive developer support, not to mention better graphics. Yet it very likely won't have LTE when it launches. The Bionic looks to offer slightly better hardware on paper, though the gpu itself is the same as last year's Galaxy S (and therefore the Charge). Regardless, Moto has said its not aimed at enthusiasts, though we don't yet know whether this means it won't still be suited to them or not. Its a completely new platform, and may have a locked bootloader, or possibly a completely new hypervisor setup (in which case the bootloader is rather irrelevant. If one of those is the case, I don't expect great developer support, at least out of the box. But if the phone does everything you need it to as is, you may not feel the need for developer support. It looks to be using a Pentile qHD display, which most people don't like nearly as much as the S-AMOLED+, though the technology certainly has a lot of fans in this section. We still don't know for sure, as almost nothing official is out, so this phone has the potential to either be the best phone of the year, or a bit of a flop, we'll just have to wait and see.
My advice, get a Charge now and don't worry about it unless you get sick of it, which isn't likely anytime soon. By then one or both of the other phones will likely be out, and you can go test them out for yourself.