The TMO laptopstick looks like a fair deal; 4G speeds: $10 for 100MB/ $50 for 3GB prepaid.
here is a referb for $19>>> Unsupported Browser
Here is the data coverage map>>>Unsupported Browser

About your hit and miss issue...
This may be a problem with the phone:
Make sure your have the lastest firmware/software installed;
Try OTA update from your phones settings menue; Update from carriers website; and/ or contact your carrier for assistance.
Also, the phone internal antenna may need repair; take it in to your carriers repair center.

I'm just not sure I can justify dropping the bank on a fancy 4G LTE phone and a new contract with another company...plus I still have several months left on my current contract with TMo and I don't wanna pay the ridiculous early term fees.

What I don't get is why my data coverage is so hit and miss...like right now...I have full bars...and always the little "E" or "3G" symbol...and still some days it works just fine and others its like trying to watch Netflix on dial up.

Blah...is there an aircard option that will give me guaranteed consistent data coverage across the lower 48, or will I encounter the same problem with other options? I thought about just going to Cricket or somebody and buying the little USB modem thing most of them offer...but I'm afraid I'll end up with the same problem and will have wasted yet more money.

Depending on where you are driving any carrier can have spotty coverage.

If I were you I would take a look at the different coverage maps, including Verizon, and upgrade to something with 4g LTE. Depending on how many videos you watch you're going to need a data plan + tethering that doesn't get you overage charges.

I think the phone is the problem; Contact your carrier for assistance.
Maybe they can offer a wifi device for the laptop (Aircard)
You should be able to opt out of the plan you upgraded to.
When I travel and while at work, I use boingo $10 month plan.

I'm an over the road truck driver, away from home 3-4 weeks at a time. When I got tired of paying $2/hr to use truck stop wifi (when I can shut down somewhere that even has wifi) I decided to go ahead and upgrade my plan with T-Mobile to include data and tethering service so I would have access to Netflix and such wherever I happen to be.

The data speed is extremely hit or miss. Sometimes it works fine, but more often other times (like today) the best I can get is the equivalent to dial-up speed which means when trying to watch Netflix I can watch five minutes of movie/tv show and then wait 15-20 minutes for the buffer to rebuild so I can watch another five minutes and do it all over again.

I think for an extra $30 a month its not too much to ask that my data be fast enough to watch Netflix without being interrupted every five minutes or less, especially when T-Mobile is supposed to be the one carrier with speed capabilities that match Verizon.

Now, the phone is an older one, and not 4G capable. Its a Nokia 5230, and I've had it for a while. Still, even 3G speed should be sufficient for watching Netflix, and I should definitely be getting more then 20-40kbps average according to CNET's bandwidth tester (average download speed according to the phone itself is even less, usually 5-20kbps).

I am very close to terminating my contract with T-Mobile and switching to Verizon. I don't want to do that, I've been a TM customer for many years and they have outstanding customer service, but this is ridiculous. For what I'm paying per month for the tethering service I expect it to actually be fast enough to be useable.

I do not believe the problem is my computer- its a fairly new machine, Pentium dual core 2.2ghz processor, 3g of RAM, and Windows 7. I also know for 100% fact that my data speed is not being throttled due to overage- not even close. I have tried disconnecting and reconnecting to the network, I have tried restarting my computer, I have tried running CCleaner on my computer to clear out any cache data and such that might be slowing it down, I have tried all three major web browsers (Firefox, IE, and Chrome), and I even went so far as to pull the battery out of the phone and let it sit for a few minutes in case it just needed to be reset.

Is there anything I can do to make my connection faster, or is it time for myself and T-Mobile to part ways, and switch to a carrier that actually delivers the data speed they promise?

Extremely frustrated, please help.