However, I am not a pro and here is what I found challenging:
1. The depth gauge was fairly easy to use but after a while I found that I had to just nail in a course and quickly hammer the nails home. Call it user inexperience (which clearly was the case) but I ended up under-driving rather than over-driving on purpose.
2. If you don't watch the plastic nail strap or cut it off frequently, it could twist around and foul the tool, requiring a stop to fix it.
3. It comes with the "automatic" trigger function: Hold the trigger, push, and nails will pop out until you let go. I found that difficult to work with: I can see how that would be useful for roofing, but for Hardie Boards, it made me pay too much attention to trigger pull/release, rather than paying attention to quality work.
Why 4 stars and not 5: Because the single-trip (one pull, one nail) mechanism doesn't come with the tool. I had to order that from a Hitachi dealer (referred by Hitachi themselves when I called) and it cost an additional $60-$70. Porter Cable, for example, will provide a different trip mechanism for free for their finish nailers (or at least they did when I bought one). This should have been included, or at least the price not so excessive, for such small and few parts.