Does it use the same batteries as other M18 tools?

Yes. It runs on Milwaukee's 18V M18 Li-Ion batteries, so it shares packs with the rest of the platform. Larger high-output packs give the longest run time.

What nails does it take?

It is a coil roofing nailer for wire-collated roofing nails, the standard format for shingles and underlayment. Check the nail length range in the manual for your material.

Is it as powerful as a pneumatic roofing nailer?

It drives roofing nails fully and consistently, and reviewers find it comparable in normal shingle work. Very hard or thick material may still favor an air nailer.

How does it compare with Milwaukee's framing nailer?

This is a coil roofing nailer for shingles; the framing nailer takes clipped or full-head framing nails and is built for lumber. They serve different jobs and are not interchangeable.

Do I need a special battery for it?

No special pack is required, but the largest high-output M18 batteries are the practical choice. Small compact packs drain quickly under continuous nailing.

Is it worth it over a cheaper air nailer?

If you work without a compressor or need to move around a roof freely, the cordless setup is worth it. If you already run air all day, a pneumatic nailer is lighter and simpler.