Bell, Telus, SaskTel and Rogers all sell service in Saskatchewan. However, there are only two networks: Rogers and SaskTel. Bell and Telus roam on SaskTel's network.
Rogers' network coverage (http://www.rogers.com/coverage
) is not fantastic here but the major areas are covered. If you are not in the boonies much you may find it is quite adequate. Rogers also has some fantastic plans here like a recent one that is under $20 with tax and a large bucket of minutes. Note that most of Rogers' coverage is 2G here (Regina and Saskatoon are 3G) which is fine for voice and text but not great for data usage.
SaskTel's network is huge and growing. It has had a lot of growing pains as it underestimated demand for the new HSPA technology. Many new cell sites have been erected in Regina, Saskatoon, Weyburn, etc. to remedy this and service is now very good. It is entirely 3G (there is no 2G GSM coverage at all). The only downside to this is that if you want to maximize your battery life, turning off 3G helps a lot, but the fast data access almost anywhere you go is a pretty big upside. SaskTel has one plan that I really like (and use), their Talk North America plan that includes US voice and text roaming and North American long distance as well. It's great if you travel a lot.
One downside to SaskTel is that their data plans have 200 MB caps for out-of-province but in-Canada data usage. This is enough most of the time but if you are outside Saskatchewan but in Canada for very long periods of time you might find this to be limiting. Bell and Telus don't have this issue, but don't have a plan as nice as Talk North America.
Wind Mobile is coming to Saskatchewan - rumour has it they'll be here this fall. However, their initial network is likely to only cover Regina and Saskatoon. They will roam on Rogers but for an extra cost. They are not likely a good choice for travellers but will be fine for people who are usually in the big cities.
I used Rogers for a long time (9 years) and I only left them because SaskTel finally adopted decent technology (
) and I got tired of waiting for Rogers to upgrade its network here. Saskatchewan has been sorely neglected by Rogers. I strongly suspect that we'll see a large network upgrade next year, but by then I will have been gone for two years. (I suspect this because Rogers is spending big money in Nova Scotia, PEI and New Brunswick doing upgrades right now. Either Newfoundland or Saskatchewan will be next.)