I have the $30/month plan as well. The 5Gb is the limit for "4G" access. Beyond that they drop you to 2.5G (aka EDGE). And yes, their "4G" is HSPA+, which is really 3.5G, but is something the N900 handles nicely. Most times I can't tell if I'm on wifi or 4G without looking at the indicator. They've offered the $50/month plan for a while with one difference: The old plan cut your data at 500Mb, vs dropping it to a slower tier. I really wish they would offer these plans as monthly plans though, as right now they only offer the low cost plans a pre-pay. T-Mobile US tends to treat pre-pay plans as second class, and offer next to no service when it comes to plan use, call history, etc. Happily the N900 records all that in the local database.