I was like many very confused when this lens was first announced. F11 and cheap so it cannot be any good can it? It was certainly not something I considered buying at the time. Partly because of my initial thought, but partly because I prefer to try and get closer rather than play the chasing focal length game. But there are times when I would love to get a record shot of a bird that fills more than the smallest focus square. So when I saw I could get one new for under £700 I thought why not give it a go, and I am glad I did.
In the hand it is incredibly light making it a no brainier to carry around on the right days. The extend to use feature I quite like. Some have called it a faff but for the three seconds it takes to extend and lock I am pleased it is there to aid portability. Sharpness wise, I’ll post some shots so you can judge for yourself. I was quite impressed.

I ordered from HDEW here in the UK and as ever their service was excellent apart from a lack of communication via email though I cannot be sure the issue was at my end.
I wanted a few things for it, a lens hood, a foot and a case to throw it in when it is in the boot of my car. The lens hood I got was this.
https://www.amazon.co.uk/JJC-Compatible-Canon-800mm-Camera/dp/B08TWSCZLP/ref=sr_1_17?crid=3SH9QYHASRQMW&keywords=Rf800+lens+hood&qid=1674499941&sprefix=rf800+lens+hood%2Caps%2C91&sr=8-17
Really quite good for the price, fitting and locking into place nicely. Very easy to mark but I can live with that.
The bag I got was from the same company. It is a tight fit length wise making the pocket in the lid all but useless. Not too well built with a lost bit of padding with a bit of stiff cardboard attacked as the inside base. It does the job though so I suppose you pay for what you get. I’ve since seen better options but I will live with what I have.
https://www.amazon.co.uk/PROfoto-Trend-JJC-Resistant-Shoulder-Diameter/dp/B073311TRN/ref=sr_1_10?crid=2EBYF8QNWZCNZ&keywords=Canon+Rf800+lens+bag&qid=1674500183&sprefix=canon+rf800+lens+bag%2Caps%2C84&sr=8-10
The foot was more problematic. Kirk make one but it is relatively expensive and not easily available here in the UK. The joys of post brexit customs make ordering from overseas challenging at times. Next was the handle/for from ishoot. I ruled this out as there is no easy way to attach my peak design anchors. So I ordered the Haoge LF-RF800. That was a mistake. It seems the locking pin position is a bit random. The one I got was different to that shown in the picture meaning the foot faced backwards. So back that went. Others seem to have got them with the pin in the other end, very odd. Hoagie also sell their LF-RF68 which has a loose pin you can place where you want, and that worked out much better for me. Hopefully I will never have the need to remove the foot as I am 100 sure I will loose the pin. Seems a very well made but of kit though.
https://www.amazon.co.uk/Haoge-LF-RF68-Replacement-Canon-Mirrorless/dp/B09NHRCRSQ/ref=sr_1_18_sspa?crid=3N6STAGGAYPJX&keywords=Hoage+lens+foot&qid=1674500716&sprefix=haoge+lens+foot%2Caps%2C70&sr=8-18-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9tdGY&psc=1
First shots I took were of the moon in daylight, not the best subject but I wanted to play. The sky was blue in this handheld shot but I tweaked the levels in post to increase contrast and send the background black.

Than onto birds. I am quite used to 400-600mm but 800mm is hard work finding birds in flight. So to start with perched or swimming birds have been the order of the day so far.

It is winter here at the moment so light levels are probably quite low. When the sun has been showing the F11 has not been an issue.

The whole setup weight and portability wise has made getting low to shore birds quite enjoyable. The tactile elements of the lens have made locating the two dials quite easy. Hopefully the coatings are tough enough to survive the abuse I will surely throw at it. The build seems very tight too. I’ve had cheap lenses in the past that often felt wobbly. The tolerances on my copy seem really good. The extension part is solid and both the focus and control rings feel very good.

When the light has been terrible, such as with this long eared owl record shot, I have been pleasantly surprised how well the lens has performed. Especially good is the IS as can be seen here. Again, handheld this was at 1/80th in the worst possible backlit shade conditions I could have wanted for this bird. We rarely see them in the UK so was nice to get to see one

At a distance I was also impressed by the detail I could resolve on a cold and crisp morning. This is a huge crop and there was little air distortion so I got lucky.

Overall I am quite surprised by how good this lens is. I am looking forward to taking it out more. Bokeh is not the best in busy scenes such as this kingfisher, but that is to be expected. I can live with that, and I can live with the other minor drawbacks.

The only real complaint are the three switches. Carrying the lens on the peak design strap I have more than a few times had them move after brushing against me. That is something I have not experienced on any lens before. That is the only noticeable worry and I have missed a couple of shots as a result. I’ll just have to learn to keep an eye on that as I will certainly be taking this lens out a lot.