I've personally always had to use a custom renderer which calculates the cell size based off the model the cell is bound to. I've been doing some experimenting in a test project using the latest 1.5.0-pre1 and randomly generated strings for the datasource. Seems that they will size correctly if my viewcell contains nothing but a label.
List View....
<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:customCell="clr-namespace:ListViewScrollBug;assembly=ListViewScrollBug"
x:Class="ListViewScrollBug.MyListView">
<StackLayout>
<Button Text="Add More Rows" Clicked="AddMoreRows_Clicked" />
<ListView x:Name="Lv"
ItemsSource="{Binding Items}"
VerticalOptions="FillAndExpand"
HorizontalOptions="FillAndExpand"
SeparatorColor="Lime"
HasUnevenRows="true">
<ListView.ItemTemplate>
<DataTemplate>
<customCell:TestCell />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackLayout>
</ContentPage>
<?xml version="1.0" encoding="UTF-8"?>
<ViewCell xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="ListViewScrollBug.TestCell">
<StackLayout Padding="10,0,10,0" VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand" BackgroundColor="Gray">
<Label x:Name="MyLabel" />
</StackLayout>
</ViewCell>
https://dropbox.com/s/sp0c1iuwilyfvda/Screen%20Shot%202015-08-14%20at%2010.16.51%20AM.png?dl=0
But if i add a picture it doesn't seem to work.
<?xml version="1.0" encoding="UTF-8"?>
<ViewCell xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="ListViewScrollBug.TestCell">
<StackLayout Padding="10,0,10,0" VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand" BackgroundColor="Gray">
<Image Source="https://15254b2dcaab7f5478ab-24461f391e20b7336331d5789078af53.ssl.cf1.rackcdn.com/xamarin.vanillaforums.com/userpics/822/pKWUYBJT6FMN0.png" />
<Label x:Name="MyLabel" />
</StackLayout>
</ViewCell>
https://dropbox.com/s/okbjxpp850yq8an/Screen%20Shot%202015-08-14%20at%2010.21.00%20AM.png?dl=0
Anybody have any tips to getting this to work correctly?