yeah, I felt the difference immediately when I upgraded from my EVO 3D to EVO LTE. I love the phone but in terms of service it was definitely a noticeable downgrade.
The $30 plan has been ok so far. This is my secondary phone. I was in the same boat (needing to talk for work) and with Sprint roaming consuming your landline minutes I crossed the 450 min limit 2 months in a row which was very expensive. It has worked well enough but since, it is for work I am still prone to using voice calls rather than data as I am risk averse. I generally avoid being the one everyone is having trouble hearing on a conf call and I go with tried and true when it comes to work
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I was looking into tmobile because of their wifi calling support which unfortunately is not available for my Nexus 4. i have heard that it works really well. Inside my office building Sprint has really weak signal so the battery dies down really fast. I was using roam control on my EVO 3D to fix that but EVO LTE is not rooted so i couldn't use that. Raleigh area was supposed to get LTE in december but Sprint is running late as it has run into money issues which don't seem to be getting resolved any time soon (with Dish throwing in their hat in the ring as well). I did notice that there are LTE towers working near Morrisville carpentar and Davis intersection. It was about 6Mbps UL and 2 Mbps DL. Tmobile gave me about 10-12 DL and 7-8 UL in the same area.
I am looking at the new tmobile uncarrier plan which will give me unlimited minutes and texting. With 2 lines it will be $80 with 500 Mbs of data at 4G and anything above at 2G. This is fair bit cheaper than what I am getting with Sprint and additional 2 GB of data is only $10 (per line) this also includes tethering support.