I used the Trango Trek for a number of years for hiking, backpacking and the occasional snow climb. They flex too much for a step in crampon, but are fine for general purpose crampons and low angle snow/ice. I used them on the Emmons Glacier route in June, 1996, and they worked well for me. So, if you are doing something like the Emmons or D.C. route in the summer, you should be just fine. Make sure your waterproof them thoroughly. They are not a winter mountaineering boot or even shoulder season, IMO. Also a good general purpose hiking/backpacking boot if you are not a UL hiker. Very comfortable and "relatively" light.
Good luck on your climb!.
Hi again Elena,
I goofed. It was Lowa Trekkers that I used on Rainier. I replaced them with non GoreTex Trango Treks in the early 2000's. I used the Trango Treks a lot for snowshoeing and winter/spring snow climbs in conditions similar to what you will probably find on a summer climb of Rainier, so my other comments and recommendation still stand. The 2 boots have very similar performance characteristics and capabilities, with the Trango Treks being sighter by about 6 oz. If you end up with the GoreTex version, obviously disregard the waterproofing comment-stone age technology.
Sorry for any confusion my faulty memory may have caused.