I had the GX CS4i for about 1 year. It was fine, but a tad slow, so eventually I sold it.
Only used once or sometimes twice a week to fill my gun (Anschutz 9015...so it's a tiny cylinder, about 220cc).
Then I bought the Hill Evo-310 as I wanted 'something' maybe a bit better in quality.
The Hill is fine for my needs. It is better quality, and is faster.
Although with my use it never gets to the point of what I would call 'hot', I didn't like just the one cooling fan so I am in the middle of fitting another fan. Max temp had been 35°C (95°F) because at first use it pumped and pumped and was slowly filling my gun when I realised that 'this is too slow'. A quick check showed that there was a slightly loose pipe connection (well, the Hill had travelled 1/2 way around the world from UK to NZ). A quick tighten up and all was well. Now only goes up to 24°C.
Anyway...the new fan is a 120mm computer case fan that moves 49cuft of air per minute.
Once it's up and running I'll put up a photo or 2, and a temp reading to show if the extra fan is worthwhile. I can't see it being a useless add-on. I'm sure it will knock down some temp from the previously uncooled side of the pump.
The Hill as supplied has a max temp of 75°C before it shuts down. Then it restarts again once cooled down to 65°C.
That's just a 10°C difference, and can't be altered by the user. I think that 75°C is too hot before the shutting down, but there are a lot of Hill pumps out there and I haven't seen many folks complaining about failures.
I'm only adding the extra fan because I can!