the nature of asp.net is such that the first load will be slow as it has to compile the site and store it in a temporary cache.
My experience for the entirety of asp.net versions is that as long as the site maintains hits every 20 minutes or so, it will only experience this slow load 1-3 times a day during pool recycles. However I have seen some code that makes more regualr recycles, or requires them due to extremely large memory utilization, which would make it slow more often.
If you are seeing recycles more regular we can help moving you to a smaller pool or dedicated pool, and as long as it is not the code of your clients site that is making the memory usage high or pool recycle this slow load will be experienced far less.