Easy on
I haven't ridden in these yet but I have tried putting them on with riding kit. They go over my Richa Goretex gloves more easily than I thought, but loosening the draw cords on both mitts first helps. The toggles were easy to use with the mitts on. I tried them over a pair of Spada winter gloves and oddly, they were slightly more tricky to get over those than the Richa and didn't fit as well. Generally there seems to be enough room to move fingers around controls, but not too much to get in the way.
Good extra layer for the wet and wind
For light rain up to an hour or so no problems at all. Rode through heavy rain and over an hour start to soak through. But for the price they are great for wind especially and some rain. Size guide accurate. Fits over normal riding gloves just fine and not too sloppy.
Simple, cheap and effective
Keep the water away and reduce wind chill, too (roughly 1/3 time longer to feel my fingers getting cold). Sizing is on the bigger side, but leaves good amount of freedom for gloves inside. Takes a moment to get used to, but I was surprised that they didn't make the steering and controls awkward. The elastic band is tight to keep well, but all is spacious enough to put on with a pair of motorbike gloves already on. They are thin/light enough to always keep in my pockets. No bad points, really. Simple and effective, easy to replace if damaged.
Great value
They won't keep your gloves bone dry but they kept mine comfortable during very heavy rain last week. You'd have no trouble getting them dry for the journey home after work, or the next day. They also keep your hands warmer by blocking the wind. Seams are taped which presumably helps with the waterproofing. Operating the controls wasn't significantly impaired by them. Great value and performance for the price. If you want 100% waterproofing then you'll need to pay for it.
Bought Medium to go over Small Spada Shadow gloves
The medium is a snug fit over the small Spada Shadow Waterproof Glove(which are no longer waterproof). Its not too baggy but can be a little bit hard to fit. Keeps the rain and wind out. Only thing I've found is they can bunch under throttle hand so some shuffling of material is needed. Overall I'm impressed and would recommend them to others.
Old gloves live again
Use these with my older gloves that were no longer waterproof, keeps the moisture and the wind chill at bay. Good if you have a distance to cover and need the extra protection, they also wrap up quite small with the waterproofs so they are easy to carry.
Good back up
My old waterproof gloves now let in water but are still useful when the weathers dry. These overmitts are easy to carry in case of rain so I don't need to bin my old gloves just yet. Bear in mind there is a knack to getting them on quickly and bike control feels a little odd at first but for temporary use they're fine for me.