Yes, GSM will activate 2/2.5G, 3G will, ofc, be 3G and Dual will use 3G when possible but allow 2.5G where 3G coverage is bad. 3G has faster Internet and won't disconnect from it while using the phone (both voice calls and SMS send/recieve will disconnect from gprs net temporarily) 2G/2.5G uses GPRS/EDGE for Internet which is slower and, yea, Youtube will be almost unusable (and some heavier websites too, - i.e. on 2.5G waiting for Gmail in browser to load in full mode is a pain), SMS and phonecalls will disconnect you from the net (and auto reconnect afterwards) So use the 2.5G instead of 3G because of the slower battery drain. IM programs work great on 2G and it won't eat your battery so fast (you can go full day being always online) - so you're always connected. I don't even use SMS anymore. You can also view lighter websites (talk.maemo.org, for example, works just fine) - and switch to 3G when you need the speed (or use Wi-Fi)