I have a heavy image site hosted on Windows Azure. The basic performance is great, but the response time for image thumbnails, which make up the bulk of page sizes, is quite variable. I use Azure CDN to serve all images, but their response time varies by an order of magnitude, and I did not find any pattern in fast (~ 150 milliseconds) versus slow (3-4 seconds) requests. This also does not look like a local phenomenon, since I tested load times from different places / continents. So far, I have come to the conclusion that the Azure CDN is just not that good, and I started looking for other ways to improve the loading time of static assets.
Now that the context is clear, here's my actual question: does anyone have experience working with services like Cloudflare and Incapsula to improve the performance of websites hosted in the cloud, such as Windows Azure? These services promise to reduce the load on the server, among other things, but I'm more interested in whether they really effectively reduce the response time for static files, and also have a negative effect on the dynamic content of the page. I would really appreciate any answers based on practical experience and / or advice for alternative solutions.
UPDATE:
Here are the response headers for one of the images on the CDN:
HTTP/1.1 200 OK
Cache-Control: public, max-age:31536000
Content-Length: 4245
Content-Type: image/jpeg
Last-Modified: Sat, 21 Jan 2012 12:14:33 GMT
ETag: 0x8CEA64D5EC55FB6
Server: Windows-Azure-Blob/1.0 Microsoft-HTTPAPI/2.0
x-ms-request-id: d7a1ef38-6c99-4b38-a9f5-987419df5d24
x-ms-version: 2009-09-19
x-ms-lease-status: unlocked
x-ms-blob-type: BlockBlob
Date: Sun, 05 Feb 2012 12:56:12 GMT
Connection: keep-alive
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