I'll be honest, I'm quite partial to the black default theme. I love having any programs that I use a LOT in a dark mode, it's so much easier on the eyes, which is why I also use the dark theme on this site.
What I'd really, really like is some sort of a search bar near the top right like iTunes has. I know you can use the Search menu under Library, which does work the same way, but this saves two clicks. I tried the Quick Search plugin, which I thought would do it. Unless I am missing something, all it does is add a text box you need to call, and upon finishing a search query, enter creates a new playlist with it.
As far as other plugins, I only have iPod manager (foo_dop)(no Apple FANBOII here, just have an 80Gig classic for the storage space lol); SACD Decoder (foo_input_sacd)(this is great for those SACD ISOs that are so elusive to me - the Pink Floyd Dark Side of the Moon SACD is AMAZING in 5.1DTS); Effect DSP (foo_dsp_effect)(I don't even use this.)
For DSPs, I use Resampler (PPHS) @64kHz-Ultra, Advanced Limiter, and Convert Stereo to 4 channels.