I'm pretty impressed with the Nexus 5. 9hrs off the charger (granted only 10 minutes screen on time) and I'm at 95% battery.
My Straight Talk (AT&T sim) gets pretty good speeds on LTE, about equal to my cable internet. Around 20 down and 5-7 up. The only problem is that on LTE I get 2 to 3 bars (mostly 2) on ground level and 1-2 bars when in my downstairs gaming/rec room (about 50/50). Decent, but it could be better. It's very slightly less than I got on Verizon LTE.
When I turned off LTE I got rock solid full bars of HSPA and speeds were around 9 down and 1 up. Perfectly usable for pet much everything whereas when I lost LTE on Verizon I was on horrible evdo does and even browsing the net was tedious. I haven't decided on whether I'll keep LTE on our go HSPA. I'd be worried about battery life impacts with lower reception, but at 9 hours for 5% in my game room on LTE, that seems fine.
Straight talk for anyone unaware is an MVNO that uses AT&T, Tmo, sprint, and Verizon towers (so ALL of the carriers) depending on the device you buy. I specifically ordered an AT&T sim card because the Nexus 5 only works on AT&T and Tmo, and my Tmo coverage is horrible. It's prepaid and my basic plan is $45 for 30 days, unlimited talk and text, and "unlimited" data. The catch is that you get 3GB at full speeds and then you get throttled until your 30 day period is over. Not bad since I've never even got close to my Verizon 4GB limit (after which you got charged a fee for each increment of more data). Pretty happy so far.