Hi Simon,
Involving your users throughout the process, especially those that contributed to the beginning research, can be a good way of showing how their time has been used and that it has been helpful.
It also depends on what you want involving them to achieve, whether it is visibility of the work being done, feedback etc.
From the extensive information gathered from the research stage you hopefully already have gathered a collective vision of where your project is going to head, what problem you are trying to solve. So any feedback that you might gain after this stage, if it isn’t usability problems (or part of testing), would possibly be aesthetic or personal related. Unless there is a large outcry, it is generally not a good idea to change your designs off these kinds of comments. If something does come up quite often, or multiple people make mention of something, you would need to actually test this to find out whether it should be impacting your design or not.
Involvement can be a tricky line, getting as much feedback and visibility as possible is great because it means that there are no surprises, people can see the process you have gone through to get to the result you have. But you also are correct, that you don’t want to get bogged down in the little details and miss the overall problem of what you are trying to solve.
I think a blog could be a good way of capturing all your design decisions and process, but you would also have to be careful that you don’t mind what you are doing being available on the web for anyone (i.e. possible competitors), and you would have to keep it up to date etc.
