Many Thanks to our testers for the feedbacks, and specially to Kyle who analyzed and proposed fixes for many of the bugs below:

Here the changes log compared to CB 1.7.1:

New Feature (13)

3242 J2.5: Gracefully deprecate old setting for tabs and users-lists for group access towards View Access Levels
3238 J2.5: Backend: User management: enforce all Permissions as com_users does
3235 Add type="viewaccesslevel" to CB XML params
3231 J2.5: Lists: Implement VIew Access Levels (keep existing Group-based access for backwards compatibility)
3230 J2.5: Backend: Fields, Tabs and List management: enforce Edit Permission
3228 J2.5: Tabs: Implement VIew Access Levels (keep existing Group-based access for backwards compatibility)
3225 J2.5: Backend: Plugins management and Edit: enforce permissions for Configuring for installation and Edit and Edit State for plugins editing
3210 API: pagination in backend should have parameter for entries/page drop-down values
3179 Joomla 2.5 support
3166 API: CBUser::unsetUsersNotNeeded( array $userIds ) needed to clear cache
3070 J2.5: language filter support for CB menus and Itemid's
3054 Backend XML API: Javascript IF statements on multiple valued list and checkboxes do not work
2903 J1.7: Limiting backend access using joomla 1.7 ACL

Bugs fixed (37)

3239 J2.5: Super User detection needs to be adjusted as multiple groups can have Super User Permissions
3232 Backend: View lists shows also lists above the admin's level, and Edit list: all groups are proposed instead of hiding groups above the admin
3227 Backend: Plugins Management list: custom View Access Levels are not filtered to display only available plugins for the admin's view levels
3226 Backend: Plugins Management list: custom View Access Levels are not correctly displayed
3224 Backend: Edit tab: all groups are proposed instead of hiding groups above the admin
3223 Backend: Create user : Email ajax checker does not check if email is already registered
3222 J2.5: Backend: User edit: Groups assigned to a user not selected
3221 J1.5: CB 1.8 B2: Backend & Frontend JUser load error
3219 J1.0/M4.6 : CB171 modules do not install on Joomla 1.0 and Mambo
3206 J2.5: Author tab access level check works correctly only for system-default access levels
3202 IE9 is displaying span elements in non-standard
3172 CB API: if $user is reloaded from database during saveSafely() there is a fatal error on _cbTabs
3165 API: if advanceNoticeOfUsersNeeded() is called before getInstance and does not contain the id, getInstance returns null
3156 API: getField for radio and single-select field types: PHP, XML and JSON modes return array of the values instead of the value
3145 Backend: Avoid floating div wrappers when no toolbars to display for better printing in safari
3136 Update required profile avatar field via profile update does not give rejection error on non extention filename
3128 Joomla ACL group names not translated in CB User Manager
3127 CB Mass mail: stops on invalid email addresses instead of continuing with displaying error
3114 Forgot login username and password same time not functional
3111 Advanced search (and admin search) on checkbox CB field-type not working properly
3108 Duplicate titles of fields not displaying in userlist backend
3093 CB mail sets Sender overriding host set value
3080 Custom setting for "Not a valid input" cannot be translated and default string is missing in default language file
3067 BCC fails to send
3053 Displaying div-based view-type forms does not format the fields side-by-side
3052 replacePrefix not working properly in some cases
3045 CB Menu message drop-down empty when no PMS and mailto link set
3044 allowaccess does not accept gid arrays
3038 J2.5: get_user_permission not checking full access tree
3037 Calendar language file included with e.g. fr_FR folder different from CB-standard fr_fr folder
3000 J2.5: CB User List access only checking one ACL group
2994 Forum tab publicly viewed shows registered only category posts
2981 Tabs groups permissions logic should not be applied to super-administrators in backend
2971 J2.5: Plugin access checking for usergroup and not accesslevel
2967 CB 1.7.1 Lost username request generates password reset process
2965 Calendar drop-downs not displaying arabic characters properly
2960 CB 1.7.1 substitution check uses language string value instead of stored field value

Details are on our tracker: forge.joomlapolis.com/projects/cb/issues?query_id=39