How do traditional track officers feel about mustang officers?

It’s like with all ranks, seen good, seen bad, and seen meh. Really depended on what they brought to the table. Some thoughts on a few pitfalls:
- sometimes they can be trapped in old paradigms
- sometimes if they were NCOs, they gravitate there. At company level this is problematic. There can only be one first sergeant. At BN level it’s toxic. There is one CSM.
- refusing any help, advice, or new information, ‘cuz I used to be a <insert MOS that doesn’t apply to the problem at hand> and I know it all’

I generally liked prior service officers and worked well with them.

I'm a Mustang. The issue I noticed was due course officers were at times jealous as they knew I had more experience and knowledge. The perception was I got the better assignment, hence a better track towards fruit salad. The ENL community sometimes were leery because they assumed I knew all their tricks. In general, those who fixate on the mustang thing tend to have a concern about their own prospects and abilities. Those who are hard chargers, competent, etc. usually could care less.

ROTC: Seen both good and bad. Some have a chip on their shoulder and expect their non-prior peers to pay homage to them for any tidbits of wisdom themy my provide. The good ones are more open and team-oriented.

Like all people though, you have to assess each individually. The important thing is to follow the golden rule, always maintain the high ground, and assist when possible.

The way to get ahead is not by bringing others down. It is to find your nitch and cultivate it to the point your superiors find that your craft is indispensable to their success.

Good luck.