I used StraightTalk (tmobile) for a month on an iPhone before getting my Nexus. If you end up having to cut a normal sim like I did, go to an ATT store or something and ask them to do it for you. Or be REALLY careful. It's really easy to get it just a little off so that the Nexus doesn't see it.
If you're willing to find all information you need online, feel free to go for ST. Their customer service and help is very under-trained and don't really know what they're doing. It took them a whole weekend to get my sister's sim working correctly. I have decent T-Mobile coverage, so I switched to T-Mobile's $30/month plan. They ported my number in under 15 minutes and know what they're doing. I use the Vonage app to make wifi and 3G/4G calls because it can display my number as the caller ID without any porting or special steps. Vonage has actually been more clear than any direct phone call I've made with ATT, Tmobile, and StraightTalk/tmobile. I no longer have to frustrate people and say "What?" 3 times in a row.