“no end” and “to no end”

I would stand that on its head and ask. Is "This amuses me to no end." as acceptable as “This amuses me no end.”? And if it is, do they mean the same thing?

"No end" is an idiomatic expression meaning something like "a great deal" and can be used as a noun - "She had no end of stories to tell." (The Free Dictionary)

and also adverbially:

"it pleases us no end"- Merriam-Webster
"this cheered me up no end" - Oxford Concise
"Her English has improved no end" - Macmillan
"Your letter cheered me up no end." - Longman

I presume you are using "This amuses me no end" in a similar way, to say that it pleases you a lot. I can see no examples in those dictionaries of "to no end" being used in this way.

It would rather change the meaning to something like "This amuses me but not to any good purpose". Of course if this is what you meant in the first place, then in my opinion the answer to your question would be no, as it would completely change the meaning. But not everyone agrees.

There's a discussion at Motivated Grammar, where Gabe asked readers if these two sentences were acceptable, and if so was there any difference in meaning:

(1a) The crank insulted me to no end.
(1b) The crank insulted me no end.

Many people answered that they were both acceptable, but that the meanings were different:

(2a) The crank insulted me without a goal or without achieving anything.
(2b) The crank insulted me endlessly.

That's how I'd see it myself, but not everyone did, and Gabe himself thought he'd use "for no end" in the first one, and I think in fact I'd prefer "to no good end". Some also saw the two expressions as synonymous.

http://motivatedgrammar.wordpress.com/2009/02/19/following-up-on-to-no-end/

It does not follow from the fact that some blogger ( a self-appointed crusader against prescriptivism, no less! Be still my beating heart!) and a small minority of his correspondents are ignorant about certain English idioms, that those idioms can mean whatever you want.

"No end" (without a preposition) is a well established idiom meaning "a great deal".

"To no end" means "to no purpose" or "to no significant effect". So far as I can see, it is not an idiom at all, but entirely literal, although it may confuse some because it uses the word "end" in one of its less common senses.

Both expressions are correct English, but they mean different things. If you mix them up, you will be misunderstood by competent English speakers.