Thanks for your interest in the product. We do not publicly disclose open air performance numbers because they tend to vary quite a bit depending on the surrounding conditions. We do get higher performance numbers as part of our internal testing in clean air environments. However, what you observe currently seems to be within a reasonable margin of what we can expect in a standard open air environment. Be confident that we continuously thrive to improve on the product performance so it may improve overtime with software updates.
That said, there are few things you need to take into consideration when comparing products, especially the Cisco 1852:
1) Instant On continuously inspect the traffic to provide visibility and breakdown of what application are running on in your network. This definitely reduces the raw performance, but has the benefit of having a better understanding of your network utilization.
2) Even though they are both 4x4, the Cisco 1852 is at least 2-3 times more expensive than the Aruba Instant On AP15. Therefore, we believe that you get more than an adequate price/performance ratio especially with our simplified interface, remote and mobile management of your sites, a number of additional features and benefits, and more to come in the future.