T-Mobile is making changes to its new 'unlimited' plan, but it doesn't fix the biggest issues

T-Mobile on Monday announced a couple of changes to its "T-Mobile One" mobile data plan, just days ahead of its scheduled launch.

The revamped plan was met with some hostility when it was unveiled earlier this month, in large part due to the way it approaches video streaming and mobile hotspot data.

Originally, T-Mobile said the One plan would provide "unlimited" 4G LTE and hotspot data starting at $70 per month, but that the former would cap all streaming video over its mobile network at a 480p resolution (i.e., not HD), and that the latter would only allow hotspot speeds up to 128Kbps (i.e., horribly slow). You'd have to pay another $25 per month to enable HD video streaming, and another $15 per month to get 5GB of LTE hotspot data.

Today's revisions address those concerns, but only somewhat. Now, T-Mobile says it'll offer One plan users the option of "HD Day Passes." The carrier says those who want to stream mobile video at a resolution higher than 480p can do so for up to 24 hours, for a $3 fee.

While that's a little more flexible than the previous all-or-nothing rates, it doesn't change the way T-Mobile will charge users to not have their video streaming capped. That idea, combined with the fact that T-Mobile is eliminating all its existing (read: uncapped, and potentially cheaper) plans with One's introduction, is what's raised net neutrality concerns since the plan was announced.

Beyond that, T-Mobile says the One plan will offer hotspot speeds of 512Kbps by default. That's still very slow by modern standards - it's much closer to 3G than 4G - but it's at least a little more usable.

There's a catch, though: In exchange for the increased base speed, a T-Mobile spokesperson told Business Insider that it'll no longer offer the $15 monthly option for 5GB of LTE hotspot data with the standard One plan.

Instead, you'll have to pay up for the carrier's new "premium" plan, which it's calling "T-Mobile One Plus." That's replacing the HD video add-on fee that was announced alongside the One plan - it's here pitched as "unlimited HD Day Passes" - and now including unlimited 4G LTE mobile hotspot data alongside it. Again, it'll cost an additional $25 per line, meaning it'll start at $95 per month.

It's also worth repeating that, technically, the One plan isn't actually unlimited - T-Mobile says customers who use more data than 97% of other customers will "have their usage prioritized" and "may notice slower speeds during times and places of congestions." You'd currently have to use more than 26GB of data per month to hit that, though, which is a lot.

Lastly, T-Mobile says it's pushing up the One plan's launch date. It'll now take effect on September 1, five days earlier than expected. A T-Mobile spokesperson told Business Insider that the change was due to "store and online traffic [breaking] records last week."

As a reminder, existing T-Mobile customers will not have to change plans come that date. New ones, however, will have to consider how much HD video streaming and hotspot data is worth to them.