Where else can you boof granite drops, kick it at the beach, and then go wine tasting on shuttle? Trout Creek feels surprisingly wild considering how close it is to Summerland. And while there are several clean bedrock rapids, this run will never be a classic due to the wood situation and a healthy dose of mank. It's worth doing if you're into exploring microcreeks, but probably just once.
The Okanagan creeking flow window is indeed fleeting, and you're most likely to catch this one in May or June, after peak freshet but before flows dry up. The best way to gauge flows is to go to the Trout Creek Trestle in Summerland. If the canyon under the trestle looks reasonable, the rest of the run should be fine too. There is an online gauge on a tributary high up in the watershed; a flow of 0.4cms on that gauge equated to an acceptable low flow (CAMP CREEK AT MOUTH NEAR THIRSK (08NM134)). The Ashnola gauge might also give clues as to what is happening in the region. While more flow would probably be more fun, you'll need to catch many small or nonexistent eddies above riverwide wood.
Shuttle is pretty straightforward: put in at the Summerland Rodeo Grounds, and take out at Sun-Oka Beach Provincial Park on Okanagan Lake. Walking or biking the shuttle is actually quite pleasant, by using the road to the Summerland Ornamental Gardens and the Kettle Valley Rail Trail.
On the river, you'll spend most of the time boat scouting and keeping an eye peeled for wood. There are a few narrow canyons and tight bedrock drops in the 1-2m range; you can get a decent look at them from near river level. Where the river canyons up, some of the drops are surprisingly fun for a creek of 5-10cms. Where it opens up into a bouldery riverbed, it's pretty mediocre. The rapids are really more in the class III-IV range. The IV+ rating is just due to catching microeddies above wood, a few pinny rapids, and some canyon commitment factor. In 2020, in addition to ~10 river wide logs, there was one large riverwide logjam, as well as a known landslide near the Summerland Golf and Country Club. Some of the jankiest rapids are actually the two just downstream of the trestle. Paddling out to the lake makes for a unique finish.