Reordering columns and hiding/showing them was on the todo-list (and still is). However, the feature that is ready for that, was incompatible with other features we are using, which made it very complicated. We will have to write quite a lot of tricky code for this, which can be done. But we decided to release the new VGPS version now when it had everything that the old system had. Then improvements will come with time. Sharing lists is half way there for example.
Corrected coordinates is on the TODO-list. Again, the old system didn't have it, so we released without it, since it didn't make anything worse.
We will consider using icons for type and/or size. While it makes the interface slicker in one way, it will make the search/filter trickier. It is not likely that we will spend time on making the filtering use icons, and then people will need to know what to write to find a mystery cache (which would be 'Unknown Cache'). Filtering with icons may be possible, but most likely a lot of work.
I do not understand the exact issue with the filtering regarding cache name and difficulty. One is a string and one is a float. It's natural that the compares aren't the same? For the boolean fields we will implement a better solution. Haven't tested it yet, but I think we can manage a select box (yes/no).
I don't think we can have the filters themselves visible since one can build quite complex filters. But some form of indicator sounds reasonable. We will try to fix something.
Creating PDFs could be interesting, something we have thought about. But every user will want different layouts. I do have some thoughts, and if you are interested, we could design layout number 1 together. Our receipt on payments are pretty much written in HTML that then gets rendered as a PDF. I would like something similar, and if you are interested in designing a layout, I can give you some pointers to what we have used as technology. Then you can probably do the template yourself (and get exactly what you want).
PS! I got a lot of new notes on the TODO-list from this.
PPS! I do realize these are suggestions and that you do understand that we might have some of it under development.