Certainly sometimes it happens, but I haven't heard of it happening more often recently. The staff generally keep a close eye on their metrics. Can you quantify how many requests you're sending and how often you're seeing "Service busy" in response? Do you send a lot of requests at some particular time (especially if it's near 0-minutes-after-an-hour) or are they spread out throughout the day?
I wouldn't expect occasional errors to be "quite disruptive"; most clients will just try again later like it says (and so many users probably wouldn't even notice unless they happen to be looking at their logs). Can you clarify what client you're using and how needing to retry later is so disruptive?