Okay, if you're going to spend 8$ on a 3g critter keeper, have you considered just getting a 10-12$ 10g tank at walmart/petco/petsmart? You're getting a lot more room, you can put a hood on it if you want since it's a regular tank, and you can easily filter/heat it without any issues.
I don't have any problems with the KK's, I've used them before, but for the price, I want as big a tank as I can get for money. I've just found them to not be a great value in terms of gallons/price ratio when compared to a cheap 10g. :)
Just wanted to point that out as an option, though either one will work for you, it's just personal preference on your part. :) No harm, no foul whatever you decide. :)
But really... lol... I started with 10g's then upgraded to 20 longs (and with the petco 1$/g sale you can't go wrong!) and divided them and ended up realizing they were my preference. :) Everyone has lots of room, it's just one heater and one filter...and life is so nice. ;)