I had originally used VPI to insure my two dogs dating back to around 2002 but switched them to Trupanion about two years ago after reading an article in Consumer Reports. I am so glad I did this!! In my experience, Trupanion has much better coverage.... no caps on expenses for an injury or illness and and the coverage and deductibles don't change as my pets get older. This is a huge benefit compared to VPI.
In addition, Trupanion emails me through every part of the claim process, has taken the time to call me regarding specific claims, and overall has been very helpful.
My only additional comment is that the "90% coverage" is a little misleading. When my dog developed cancer, I took her to a specialist. While they have covered 90% of her treatments (minus the deductible) so far (some are still pending), the initial $200 consultation was not covered. Ultimately, this doesn't make a difference... I would still have taken her to the specialist and I would still use Trupanion! (And to be fair, I may have missed this in the fine print print of our policy.) I just remembered from the website the "90% coverage" and this wasn't quite accurate.
Overall, I have been very happy with Trupanion and I have already recommended them to several friends with pets.