The feature set of GetFLV is very promising. It supports many FLV sites--not just YouTube--allows you to add your own, and even allows grouping by category. You open your chosen site in the built-in tabbed browser, and click to run a video. The program detects the video is starting, and offers to capture the stream for you. You can also right-click to download the linked video directly. Multiple simultaneous downloads are supported, a very useful feature. The built-in FLV viewer is functional but sometimes sluggish about moving rapidly through a file. Last, and perhaps most usefully, it will convert videos to and from .flv format.
In my testing, GetFLV worked on the built-in sites and on some other test sites I picked. Downloading was slow, but that can be the result of the source sites. There is no option to set maximum or minimum bandwidth.
Indeed, lack of options is an issue. GetFLV's interface is sparse and non-standard. Font use, spacing, and general layout are all very bare-bones. Some things are odd--to close a tab, you must right-click instead of there being tab-level close boxes. It's not always obvious which functions are single-click and which are double.
All that aside, GetFLV is the most functional FLV downloader I have personally tried. It is not site-limited as others tend to be, and it includes good tools for organizing both source sites and your library of downloaded files. The trial is certainly long enough to determine if you can live with its quirks. The price is a bit high for a utility program, but if you often use FLV sites, it could be well worth it.