Sasktel has been recently bragging about their new "3G+" network. For a change, it actually is something worth bragging about. Cell phone technology is extremely complicated. There is an old saying that the good thing about standards is that there are so many to choose from. Cellular network people have taken that idea to a whole new level.
Johannes Lindenbaum has a pretty good explaination of the situation. In summary, Sasktel, Telus, and Bell are all deploying UMTS/HSPA networks that use the 850/1900 MHz bands. New phones will have SIM cards and so you can switch phones just by moving the SIM card. People in other countries had this feature with their GSM phones for long time already (many places it is required by law). We North Americans are a little slow.
The buzz is that Sasktel is selling SIM cards to be used with unlocked phones. This is much bigger news than the supposed superior data speed of the "3G+" network, IMHO. People have already been buying iPhones elsewhere and then buying a $10 SIM card from Sasktel to activate them. Obviously you still have service fees but being able to buy and sell phones and easily move them between providers is a huge deal.
Want to buy a phone to use on the Sasktel 3G+ network? Minimally, it must support UTMS on 850 and 1900 MHz. That will give you voice service. Watch out, some phones support GSM on 850 and 1900 and UTMS on 900 and 2100 and sometimes the labeling can be confusing. Most UTMS/HSPA networks in the USA use the 900/2100 bands and those phones will not work. AT&T uses 850/1900. The phone should support HSPA if you want data services (I'm not sure about the difference between HSPA, HSPA+, and HSDPA). The phone needs to be "unlocked". Because phones are often sold at a loss, companies lock them to a single SIM card so they have to be used on a certain network. Courts have ruled that it is legal to break this "lock" (usually you just need a numeric code) so you can use any SIM. If the phone does not come unlocked you can usually pay someone to unlock it for about $20.
One final note, you don't need a "smartphone" (another marketing term) or a data plan to get on the 3G+ network. All you need is a phone that supports UTMS on the 850/1900 Mhz bands. Finally take this information with grain of salt. I'm not an expert so do your own research before spending big money on something like a Nexus S. ;-)