It's pretty simple.
1. HSPA+ and LTE speeds are fairly similar so lack of LTE isn't really an issue.
2. Build quality is vastly superior over current Samsung devices.
3. Unlocked without a contract opens up many options for phone plans. ($45/month unlimited everything in Straight Talk).
4. Can't stress how important the lack of contract and carrier lock is, so I'll list it again. This also means no restrictions on tethering, since there's no carrier lock to get in the way.
5. True nexus without carrier interference.
While many people bemoaned lack of LTE, HSPA+ speeds near or the same as LTE in most markets, and exceed LTE in some markets. It's not even a fair comparison, The N4 greatly exceeds expectations and blows Samsung build quality out of the sky.