Recently we upgraded from XenApp 7.5 to 7.6 and figured out that the logon experience is worse with 7.6 when starting a published application (i.e. Internet Explorer).
In the meantime, Citrix published a hotfix (ICATS760WX64009) that solves the issue: http://support.citrix.com/article/CTX142036
It’s even a bit faster compared to 7.5.