Google has described the Nexus 4's lack of LTE as a "tactical" decision, noting the limited availability of LTE outside of the U.S. along with the increased cost and decreased battery life the technology tends to deliver. So is the lack of LTE a deal-breaker? That's up to you to decide.
Personally, in most typical day-to-day phone-based usage -- Web browsing, social media use and the like -- I find it tough to tell the difference. (Some analyses have actually found T-Mobile's HSPA+ network to be comparable to or faster than LTE networks in parts of the country.) Remember, we aren't talking about 4G vs. 3G here; we're talking about 4G LTE vs. 4G HSPA+.
(You may also want to consider that owners of last year's 4G LTE Verizon Galaxy Nexus have found that the carrier-dependent configuration comes with some troubling caveats -- namely, delayed upgrades and software interference -- that directly clash with the "pure Google" promise of the Nexus brand. As someone who's used both a Verizon-bound Galaxy Nexus and an unlocked HSPA+ version of the phone, I've found the latter setup to provide a much better overall experience.)
In terms of actual phone calls, the Nexus 4 performed admirably in my tests. I could hear voices loud and clear -- so loud, in fact, that I often had to turn the volume down on the phone -- and people with whom I spoke reported being able to hear my voice fine as well.
The phone's external speaker is sufficiently loud, too, with more than enough volume to handle calls and music alike. When I tested the Nexus 4's speaker alongside the Galaxy Nexus's, audio played through the Nexus 4 was significantly louder and clearer-sounding with both phones at their maximum volume settings.
The Nexus 4 supports near-field communication (NFC) for contact-free sharing and services. Those services include the Google Wallet mobile payment system, which comes preloaded on the device.