I'm just going to list out what I want to see new or fixed in 5.2...so here's the list in no particular order.

So clearly this isn't a list of what everyone wants, and we most likely wont get many\any of these :)

• Content filtering fixed: Ok so lets use the download widget as an example.  You can narrow the filter selection by categories and tags right?  Nope :)  The filter is using an OR, where it should be an AND...like "Give me only items with this category, and ALL of these tags".  Or at least expose the ability to change it...
• Document list widget, expose the new template buttons every other widget has
• Module builder: Taxon filter in the backend list
• Module builder: Sorting\Filtering...this needs NEEDS to be there, heck even in 5.1 SP1
  
• Module buider: one->many link (5.1 gave us one parent->one child)
• Module builder: Stongly typed...types :)  So backend "sample" code to generate it, or thunder generated.  Bonus points if the samples knew that you had the typed class available and could adjust the sample.
• Designer support for more than the two out-of-the-box taxon types...I want to add my own and have them be usable w/out coding custom widgets.
• Editing of the config XML directly in the UI (some of us persist the configs to the DB, so editing isn't that easy once the column size exceeds a certain length).  I know settings has most covered, but I can't re-order settings nodes, or edit the module builder xml in there.
• Telerik Reporting update...if you use it, then give us the latest version, or somewhere near the latest version
  
• Are you still reading? 
• Policies need to work again, this ties into the "granular" permissions promise.  We can't right now say "People in this role get these widgets", etc
• We have MVC now to generate cleaner markup, I'm sure the support for that will improve as time goes on, but it'd be nice to have some existing control support to clean-up the often obnoxious mark-up.  
• Working CDN, no duplicate jQuery
• A real Script Loader...search the forums for trouble loading jQuery, there's a lot of results\views.  You know where you don't see that kind of thing?...jsFiddle :)  What would be nice is to make it an option on the template itself.  So you can drag\drop\reorder (kendo can help with that) the scripts this template needs to load and in which order...AND if they'll render in the header or at the end of the body.  It's be nice to create script bundles here so you can say like jquery and kendo top, plugins bottom (or something).  Developers and designers are annoyed by this, they shouldn't have to be.
• This will happen no-time soon, but start to move away from msAjax...kill that crap, or at least start
• Embed Kendo.web and .dataviz as well as .all...all is getting too large.
• JSON.Net date formatter\serializer instead of the crappy WCF date format, kendo needs this.
• Ajax Loading icons, come on, these need to be everywhere.  I can't tell you how many times I've sat over someones shoulder and they click on a button and it (appears) to not do anything b/c the service callback hasn't happened yet.