I'm currently working on a murder mystery set in Victorian London. I hope to publish it in the New Year.
From a research point of view, Victorian London is an excellent setting for a novel. There is so much material available online. I've been able to do all the necessary research without stepping away from the computer. Pre-internet, it might have taken months or years to find this amount of information. And then one would have to photocopy it, or transcribe it by hand.
On the other hand, from a research point of view, Victorian London can be a bad choice of setting because there is so much material available online. There is always more research that can be done. This is true of course even when the subject is not Victorian London and whether one is talking about a fiction or non-fiction project. One can spend forever researching and never get around to writing anything. But it is much easier to procrastinate when the source material is a click of a mouse away at any time of day or night, rather than requiring a journey to a record office which is only open for limited hours.
It's also possible to become excessively bogged down in detail. I work on the principle of 'if you can't find out, leave it out' and gloss over minor points if they aren't essential to the plot. The main thing in historical fiction, I think, is to be true to the time and place and the mindset of the people who lived in it, rather than obsessively trying to recreate the period by describing every little detail.
Even when I have been able to find out something, I sometimes ignore it! I've been able to discover the exact layout of a particular location I'm using for a key development of the plot. On referring back to it, having written the chapter, I've found that the action I've described doesn't quite fit the layout. I've decided that artistic licence is permitted here. My plot is not affected one way or the other. The location no longer exists (although I have Google Earthed the place where it was, and I may go and visit it one day) and it would have to be a very nitpicky reader who went to the trouble of tracking down the source I've used and comparing it with what I've written.
I also have a minor plot problem. I need a fairly minor incident to occupy my character away from the main storyline for a short time. I had an idea for this, but have decided it's good enough to develop into a story in its own right. So it's back to the planning stage on that one, and a bit more reading round the subject to see if anything inspires me.