Picture makes it obvious
I used to use HP for a large-ish office network in one of my "previous lives".
It did the job and did it fairly well. However it had a major problem- it "breathes" on the sides. The pictures look like HP has failed to rectify this problem till this day - there are a grilles on the sides and there are fans behind the grilles.
Airflow sidewise? In a rack? No thanks. I have actually seen fires started from that (not HP, Ascend 10+ years ago).
To add insult to injury the side fans do not look like hot swappable either (at least from the "service" front). By the way I know that HP provides free "lifetime" replacement for these (or at least used to). However if I run an operation I'd rather pay for them as spares than have downtime to disassemble a switch and replace them.