As a matter of policy I like to cover as many forms as is reasonable, as a lot of apps/systems/etc. are doing searches based on the glosses.
I should have applied the "can it be the subject of a sentence" test to 'good value'. Of course, you can actually say "Good value is one criterion I apply when choosing a restaurant." That test was often invoked by Bart Matthais on the SLJ group - if you can't say "XXが..." it isn't a noun. I note that many terms in 大辞林 which are marked as "名" fail that test.

Sorry to make such a fuss over a hyphen. :-) I didn't think think that having a hyphen was 
necessarily wrong. I just felt that it was preferable to have the two-word spelling if only 
one spelling was to be included. It seems that Webster often gives only one of the correct 
spellings for adjectives that are spelled two ways.
e.g. Webster has only "up-to-date", whereas the Chicago Manual of Style says:
.
* Adjectival phrases: Hyphenated before a noun; usually open after a noun
- an up-to-date solution
- his equipment was up to date
.
... whereas Wiktionary does include two spellings, as you have done for this entry (お得):
up-to-date
up to date (after the noun)

Jim, you should write to OED and set them straight :-) ... because those sentences are all quoted as 
illustrative of OED's definition of "good value" as an adjective: 
"worth the money spent; (in later use also colloq.) entertaining, worthy of interest or attention".
.
In addition, Wiktionary labels "good value" as an adjective, and Collins has the following entry:
* cheap (adjective) costing relatively little; inexpensive; good value

Well, let's have both then. (All those OED examples were nouns...)

@@ -24,0 +24,1 @@
+<gloss>good value</gloss>

お徳: 284254
お得: 22976441
御徳: 2627
御得: 5216

@@ -4,0 +4,3 @@
+<k_ele>
+<keb>お得</keb>
+</k_ele>
@@ -8,1 +11,1 @@
-<keb>お得</keb>
+<keb>御得</keb>
@@ -12,3 +15,0 @@
-</k_ele>
-<k_ele>
-<keb>御得</keb>

Not all two-word adjectives are hyphenated. 
And even adjectives that are hyphenated when they precede a noun may be unhyphenated otherwise.
Certainly, "good value" is unhyphenated when it doesn't precede the noun it modifies.
Also, it seems that it is not usually hyphenated when it does precede the noun it modifies.
.
I. As an adjective NOT preceding the noun
In the example which prompted my submission, it would be wrong to hyphenate.
その他に便利な乗車券もたくさんあるので滞在期間中に何度も利用をお考えの方にはお得ですし、おすすめです！
Here, they are saying "Those other cards are good value."
There's no hyphen there – see the Wiktionary and OED entries below.
.
"When a compound modifier follows the term to which it applies, a hyphen is typically not used. For example, 'that gentleman is well 
respected', not 'that gentleman is well-respected'."
http://en.wikipedia.org/wiki/Hyphen#Compound_modifiers
.
II. As an adjective preceding the noun
Even when the compound adjective precedes the noun, "if the compound is a familiar one, it is usually unhyphenated." [Ibid]
And this seems to be the case with "good value". Try a Google search for "good-value glasses" or "very good-value meal", for example. 
It's hard to find hyphenated examples.
.
III. References
1) Wiktionary @ good value
Adjective
good value (not comparable)
Used other than as an idiom: see good,‎ value. 
http://en.wiktionary.org/wiki/good_value
.
2) OED
good value
worth the money spent; (in later use also colloq.) entertaining, worthy of interest or attention.
1842 What rent did he receive from the former tenant? Was the land good value at that rent?
1869 The late agent said it was good value, little cabin and all, for 7s. 6d. a year.
1920 If I could get Philip Langdon to talk to me about affairs he would be good value as he knew everything about politics.
1937 The geyser was better value, it went off.
1961 Her eyes shone with excitement. Either the Garlettas were exceptionally good value or she was longing to get out of this house.
1987 Wholemeal quiches are good value—consult the blackboard for daily specials.
2001 With Mike Catt in effervescent form, scoring two second-half tries..Bath were good value for their win.

I don't agree. It's an adjective, so the hyphen is correct.

@@ -24,1 +24,1 @@
-<gloss>good value</gloss>
+<gloss>good-value</gloss>

@@ -24,1 +24,1 @@
-<gloss>good-value</gloss>
+<gloss>good value</gloss>

koj, meikyo entries for とく confirm that they're they overlap for this meaning

@@ -9,0 +9,6 @@
+</k_ele>
+<k_ele>
+<keb>御徳</keb>
+</k_ele>
+<k_ele>
+<keb>御得</keb>

http://q.hatena.ne.jp/1102465876
Eijiro (よりお得 : better value, お得な値段 : great price)
GG5: お得コース an economical [a money-saving] plan.

Seems to be interchangeable. Merging  2739990 submission.

@@ -7,0 +7,3 @@
+<k_ele>
+<keb>お得</keb>
+</k_ele>
@@ -11,1 +14,2 @@
-<pos>&n;</pos>
+<pos>&adj-na;</pos>
+<pos>&adj-no;</pos>
@@ -13,0 +17,2 @@
+<gloss>bargain</gloss>
+<gloss>good-value</gloss>