I have a Treo 650. I pair it with my notebooks to browse the net where wifi is not available.
Here are some things you need to know:
Unless you have an unlimited data plan, you will be charged per KB. They do have like 50MB plans, but beyond that you will be charged. Verizon and Cingular charge a lot for their data plans. Sprint and Tmobile are much more reasonable. US Cellular might be as well.
Bluetooth DUN is against the TOS. You can get away with it, but excessive downloading, say 500MB per month is a red flag and they will charge you. I have seen some people get bills for a couple thousand dollars. I wouldn't use the connection to download GB's of data. You will be surprised when the bill comes.
EV-DO can get between 300KB -500KB/sec. My Treo 650 is 1x, so i get maybe 80KB/sec.
Make sure the phone you get has BT DUN enabled. Some cell companies especially Verizon, cripple the Bluetooth and disable BT DUN. You would have to read up on the carrier to see if they are disabling things. Although, the Moto Q is only verizon at this point. (I think)
Do you use a Mac? If so, you may have trouble getting things onto the Q considering it is Windows mobile.
I have a recommendation for you. The Treo 700P and sprint. Sprint has the SERO program found here
http://www.sprint.com/sero. Basically you get 500min (1250 and 2500 also available) and unlimited everything (data, picture mail, IM, etc.), No roaming. If you go over your minutes it is $5 per 50 min. Unlimited Nights and Weekedns, All for $30 a month. I have this on my 650, and it is amazing.
To get it, you have to have a sprint employees email address. Here is what I did. Go to a sprint store, chat with the guy for a bit. Then say I will be back and ask for his card. That contains the email address. And bam. You got it.
If you have any questions, PM me.