Early days but these guys have solved a major problem for me!
I moved from BlueHost to SiteGround looking for improved performance but things got worse at SiteGround - My sites kept going down with error 502, 503 and any 50x you can think. The guys at SiteGround kept telling me it was my plugins. I optimized and optimized but my sites were still going down.
Then I migrated to 20i Reseller hosting. To be fair my sites were still going down but the support guys at 20i suggested that I split my sites to use their own packages and boom problem solved - speed not diminished!
I am really thankful to the support guys at 20i for their professionalism and speed - they not only respond fast they know what they are doing and today I can say that my quest is over - so far so good!