Are any worth buying?

Only if you love Razorbeast.

Are there any specific issues or stories you'd recommend to others?

Not unless they are a completionist or BW Tragic, in which case they'll likely have them.

How do they compare to the current era of Transformers comics... and do you think they should revisit this era as a comic?

Definitely worth a revisit, lots of stories could be set in the actual Beast Wars timeline using the showcast, and the possibilities of no cast character stories are near limitless.

Comparing to the current crop of comics, the two main release books are Furman penned, so they are very easy to plot out. They are good reads, but nothing great and the Ascending was a fun romp that ties only marginally into the main BW lore. Better than the Costa and McCarthy stuff but pale in comparison to MtMtE and RiD.