Python:

No standard GUI toolkit (the community goes round and round about this but never seems to settle on anything). The evolution of tools and methods to distribute and install Python apps and libraries has been, well, rocky. (Although lately this seems to be moving closer to getting fixed.) CPython is still slow as interpreters go (although PyPy is looking pretty good these days, if it becomes the "standard" Python this problem goes away). You can't subclass built-in classes (e.g., list and dict) without overriding a lot of methods, even if all you want to do is a simple hook into an event (e.g., to hook into an item being added to or removed from the list, you need to override delitem, append, extend, insert, pop, and remove--there's no subclassable "change" event notification, nor any "protected" methods that factor out common code used by all the above methods). Up until virtualenv was invented, keeping separate Python environments for different purposes on one machine was a real pain.

Perl 5:

All the really good stuff nowadays seems to require mod_perl, which has low availability everywhere I want to go. Some really incredible functionality can be encapsulated in modules, but what is under the hood is often fragile or frightening: source filters, typeglobs, whatever Moose is doing... DateTime is brilliant but still made some very bad design decisions (not returning a stopwatch duration when subtracting two DateTime objects) Dual-lifed modules in core and on CPAN still cause conflicts module authors still put interactive stuff in their module configuration scripts so that they can't be automatically installed

Haskell:

惰性计算导致空间泄漏。 数字层次结构不是根据数学抽象构造的。 严格的单元IO会使调试更加困难。 大型实现处理I/O的方式似乎与标准不太兼容。(特别是，输出字符只输出低8位——然后构建代码，使用这个假设来执行二进制I/O。我吐!) ($)运算符的结合性可以被改变以使某些表达式更漂亮。

大多数问题都不会上升到讨厌的程度，有些人试图解决或为每一个问题构建可靠的变通办法。

编辑:关于第5点有些困惑。特别是有些人似乎认为我指的是论证的顺序，但我不是。我不解释我的意思，我只想让人们去下面的链接http://hackage.haskell.org/trac/haskell-prime/wiki/ChangeDollarAssociativity，它很好地表达了我的意思。

Python:

缺少静态类型 默认参数处理(特别是可以为未来的调用者更改默认参数的事实!) 需要的下划线太多(构造函数必须调用__init__) 缺少适当的私有成员和函数(惯例只是说大多数以下划线开头的东西都是私有的，除了像__getattr__这样的东西不是) 有趣的打印到文件的语法(但他们在Python 3中修复了这个问题)

C#

泛型参数是不变的，c# 4.0为泛型类型引入了协方差和逆变性 可覆盖的类成员必须显式地标记为virtual

Java

缺少无符号数字数据类型 基本数据类型不是对象

c# / .net:

Classes should be sealed by default There should be no lock statement - instead, you should have specific locking objects, and there should be methods such as Acquire which return disposable lock tokens. Corollary: there shouldn't be a monitor for every object. GetHashCode() and Equals() shouldn't be in System.Object - not everything's suitable for hashing. Instead, have an IdentityComparer which does the same thing, and keep the IComparer<T>, IComparable<T>, IEqualityComparer<T> and IEquatable<T> interfaces for custom comparisons. Poor support for immutability Poor way of discovering extension methods - it should be a much more conscious decision than just the fact that I'm using a namespace.

这些都是我想出来的，明天问我，我会想出一个不同的5个:)