I have suffered a serios shoulder problem which makes winching in heavy weather inful and dangerous. I considered converting my Winches to electric but cost was way outside budget. Bought a winchrite as a temporary solution and can say it is brilliant. Highly ecommended.
I purchased a 'Whinchrite' some years ago for my last boat where there was a considerable amount of friction in the lines.
Overall it was a good purchase. Not only did it take the strain out of the basic job of getting the sails in and out but it made performing a gybe easy, safe and very fast. However, when I used it on a charter boat (with deck equipment cut down to the cheapest possible) I found it was just as likely to do damage than haul the sail.
My wife also found it rather heavy and not so easy to use. In fact, in the end she wouldn't use it. I don't regret buying the winch - But handle with care.
I have to say that at £499 in the UK it is considrably more than to buy in the USA and get shipped over. Further if your need for power assistance is growing more each year thhen you need to think of either a new boat or retrofitting proper powered winches.
On our new vessel we have electric winches which are a dream, they mean we have another ten years of sailing before having bionic implants.