Is there an easy-to-use, fast genome browser yet?
It all depends on what you want to do and what you expect in terms of speed and ease of use. But I doubt there can be a genome browser that is going to be as fast as, say, scrolling a text file in a text editor. When you zoom-in/out, move region, etc the browser has to do quite a bit of computation, possibly a lot of it!
browse a 50GB whole-genome BAM file
The size of the bam file in itself does not mean much. If you want to visualise small regions of a few kb or less and coverage is not crazy high, than something like IGV should be pretty quick. If you want to visualise larger regions like big chunks of chromosomes, then BAM files are going to be slow and you may need to use bigwig files instead.
Any other recommendations?
I'm happy with the browser I wrote, ASCIIGenome, because the files I work with are on a remote server and anything with GUI is, as you say, painfully slow and moving them locally is equally a pain. Loading a bam file is just:
If you want raw speed,
samtools tview is probably by far the fastest but it's very limited in what you can do.